Behind the product: Duolingo streaks | Jackson Shuttleworth (Group PM, Retention Team)｜Lenny's Podcast: Product | Career

Duolingo is a $14 billion company that's hitting all time highs too, it just keeps going up.

I think it doubled in value in the past six months.

Streaks is the most impactful feature.

We have right now over 9 million users with a year plus Streak.

If you look at the numbers, I think has been our biggest growth lever.

What Duolingo really focuses on is, you know, how do we help users build habits around language learning?

Getting user come back the next day is the biggest problem to solve.

Let's get into the motherload of learnings from the journey of Streaks.

Talk about the key lessons insights and also wrong turns along the way.

I'd say like test everything.

We've run in the last four years over 600 experiments on the Street.

So every other day we've actually set up really good infrastructure for copy testing.

We used to say continue our like standard CTAs continue.

And we changed that to commit to my goal.

And it was like a massive win.

There's so much human psychology that you all learn through all these experiments of just like how to motivate people would motivate would be motivate.

Say that you played a mobile game that you've done it for 3000 days in a row.

I don't know. Maybe that hits a little bit different than you've learned Spanish for 3000 days.

Today, my guest is Jackson Shettleworth.

Jackson is a group product manager at Duolingo, leading the retention team.

This is a different kind of episode that I'm experimenting with, where we spend the entire conversation focused on the journey and lessons of a single feature.

In this case, Duolingo Streaks Duolingo is a $14 billion business.

Just over the past six months, they doubled in value.

They're hitting all time highs in usage and market cap.

They're also one of the very few successful and also the single biggest consumer app business in the world.

And as you'll hear from Jackson, the Streaks feature is the single most impactful feature that most contributed to this growth and success.

In other words, you could argue this one feature created billions of dollars of value, which to me means it is worth studying in -depth.

In our conversation, Jackson shares the history of the Streaks feature, all of the biggest wins and wrong turns they've taken along the way, what he and his team have learned about what works and doesn't work with a Streaks mechanic, and also how they set up their teams to operate in a way that allows

them to run over 600 experiments on this product and continue to find big wins.

I hope to do more episodes like this on features and products that you'd love to hear more about.

So leave a comment either on YouTube or on Substack and tell me which product or feature you'd love to see me cover.

And if you enjoy this podcast, don't forget to subscribe and follow it in your favorite podcasting app or YouTube.

It's the best way to avoid missing feature episodes and it helps the podcast tremendously.

With that, I bring you Jackson Shettleworth.

Jackson, thank you so much for being here and welcome to the podcast.

Yeah, thank you. Long time listener, first time caller.

So I appreciate it.

So this is going to be a really interesting conversation.

I've never done an episode like this before where we basically spent like an hour, an hour and a half going into one feature of one product, but this is a very special feature.

It's a very special product.

Have you ever spent like an hour an hour and a half just talking about this one feature with anyone?

Well, internally, so when we when we onboard new folks to the team, we'll do I actually just did this with somebody that joined the team recently where we spent and I was like, hey, let's spend an hour just talking about the streak.

We got through an hour and I got there about 30 percent of what I wanted to share.

There's just so much we'll talk about this, but there's so much that we've learned over the years, but never anything externally like this.

I think we've shared bits and pieces of learnings, but this will be like the the motherload of learnings, hopefully, how Duolingo built the streak.

We should title this the motherload of learnings of Duolingo streaks.

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Okay, so for people that don't know anything about what Duolingo Streak Start, can you just first give a brief explanation of what is Duolingo Streak?

What is this feature all about?

Well, presumably people know Duolingo is a language learning app.

The Duolingo Streak tracks currently anyway, how many days in a row you've done a lesson.

So you come to Duolingo, you do a lesson, your first lesson, you'll start a streak, and then every consecutive day that you come, use the app, you'll extend your streak.

And I should actually put an asterisk around how many days in a row, because we also have built flexibility into the features.

So we have these things called streak freezes.

It's like insurance for your streak.

So it's a pretty simple feature in theory, but over time we've layered on challenges and goal setting and rewards and social features.

A lot of our notifications are tied to the streak.

So pretty simple feature to understand, but it's been a really rich feature for us to build on top of.

Some people might be hearing this be like, Duolingo Streak, what's the big deal?

There's other people that are like, holy shit, I want to learn everything I can possibly learn about Duolingo Streak.

So many companies are trying to copy what you've learned from this.

Give people a sense of the impact that this one feature has had on Duolingo's success and growth.

This is and this is not just the subjective retention PM talking.

I think this is our biggest feature with the exception of the lessons.

And I think it's actually where to start that.

Streaks are a great engagement hack.

I'm kind of of the opinion that any team, any app out there can introduce a streak.

And if you figure it out, it probably works to retain users.

But at the core, you have to have an app that people want to use.

And people really like using Duolingo.

It's fun. It's delightful.

You learn something.

And so it allows us to layer an engagement mechanic on top of that, like the streak is really powerful.

So it ships a disgusting amount of DAUs.

Again, it is just one of our golden geese.

And again, what's cool is that you look at notifications.

Notifications for Duolingo is massive.

I mean, us sending better, whether it's copy or timing, so many of our notifications work because they reference the streak, because users care about the streak.

And so not only is it itself, us iterating on the streak, a huge driver of DAUs, but it's also something that enables other really high valuable features.

I was looking up some stats before I came on, and it's pretty crazy.

So we have right now over 9 million users with a year plus streak.

So 9 million of our users have had used Duolingo every year, almost every day, for well over a year, which is pretty, which is just, I don't know, I like to imagine things in terms of like, okay, well, if you put all these people in a city or in a place, where would it be?

And it's like a very large city, 9 million people.

So for a year have been a year long streak.

That's incredible. I was just looking at the stock of Duolingo.

So Duolingo is a $14 billion company at the time of recording this.

It's hitting all time highs too.

It's like just keeps going up.

I think it doubled in value in the past six months, something like that.

And what I'm hearing from you is streaks is this other than just like the core learning feature, which is just like the product of Duolingo, this is the most impactful feature in terms of growth and in that retention specifically.

I mean, if you look at the numbers, I think pretty objectively has been our biggest growth lover for driving DAUs.

And also say a lot of it's just related to how we think about growth at Duolingo.

And a lot of what we try to do is organic growth.

We think about growth just as much as bringing new users onto the platform is not losing them.

If you're just bringing people onto the platform, then they churn, that's not going to be sustainable.

And so as much as we can do to keep our users coming back and actually retaining as users, it's going to make it, it's going to give us a much easier base to continue growing DAUs off of.

Perfect. Okay. Talk about how this feature originally came to be.

What was the original version of it?

What was the original insight that led to be one?

So the oldest streaks are as old as Duolingo itself.

When we launched Duolingo, we launched with the streak.

And I say we, I was like just graduating undergrad when Duolingo launched.

So this is well before my time.

But we launched with a streak feature.

Initially how the feature worked was you'd come to Duolingo and you'd set a goal for yourself.

And it was an XP -based goal.

So Duolingo, a little bit of nomenclature.

We have an experience point -based system that drives a lot of our features in the app.

And the way you'd set it is you'd say, based on what your language learning goal was, maybe you have a 10 experience point goal versus a 50 experience point goal.

And so extending your streak would be, hey, can you hit 50 experience points if that's what you set your goal to be?

And this worked well.

I think this also speaks to how Duolingo initially grew.

Luis launched it with a TED Talk.

We probably had a more tech forward user base initially.

And so this whole idea of an experience point -based streak system made sense.

But what that also meant is that you could have a user come and use the app, do multiple lessons a day.

Maybe they just set too hard of a goal for themselves and then lose their streak.

Which you don't need to be an expert in streaks to understand that's probably not good.

The nice thing with how we initially set it up though is it really did connect with what your goal was.

So if you were serious, let's track how good you are at being a serious language learner.

But I'd say one of the most impactful experiments we ran was about, this is actually as I was joining or just after I joined, we had run this experiment, was to move it from an XP -based streak to just do one lesson a day and you'd extend your streak.

And the risk that you can imagine is, well, then users care less about it because it's not connected with their goal.

And we saw none of that.

I mean, this was a huge driver of DAUs just making it easier to extend your streak.

But I think really importantly is still meaningful.

The unit of use, as you're thinking about building a streak, I think it's really important to think about what the unit of use of your app is.

The unit of use for Duolingo is like doing a lesson.

And so if what we care about is users coming back every day and doing a lesson because it shows that they're actually engaging with the app, then it doesn't hurt us to make our streak focus on just do one unit versus multiple.

And so that was probably the big sea change experiment that we ran at the time was moving from an XP -based streak to a one lesson streak.

It's also simple. And I think that's one of the things to think about with streaks.

It's always easy as a PM to have a million goals or objectives for what you want your feature to be and potentially build a more complex feature.

In a one lesson streak, it's just easy for more users to understand.

Yeah, that's exactly what I was going to say.

And just for folks that aren't super familiar with XP, it's basically experience points, and you get them from doing things.

It's like... You do stuff on Duolingo, and then based on what you did and how well you did it, we give you experience points.

This actually drives a number of our features in our app.

So leaderboards is the big one.

We have a leaderboard system where you try over the course of the week, you battle with 29 other people and you want to win.

That's all driven by XP.

So we do have other features in the app that really benefit from this XP system.

This streak is just no longer one of them.

Okay, so I want to talk about the journey from that point to what it is today, but a quick tangent.

I saw Louis' tweet just this week.

Someone asked him, how do you decide whether to optimize for learning or engagement?

And he's like, no question.

Everything we do is focused on engagement because you won't learn anything if you're not coming back to the app.

As an engagement PM, that was like the coolest thing he could have ever done.

Well, again, very much as objectively, I guess, as an engagement PM.

I mean, that's how I've...

I'm sure my learning, the learning folks at Duolingo will cringe when they hear it.

I see myself as a learning PM as much as an engagement PM because the easiest way not to learn on Duolingo is not to come back the next day.

And so if we don't make the app retentive, you will have no opportunity to engage with our learning features.

Now, I do think that there is a long tale of learning where if you start to dumb down, and honestly, this is something we wrestle with the streak as well, you start to dumb down the experience and your users aren't actually learning.

They're not going to care.

I mean, streaks work best when they're sitting on top of an app that users care about.

But, yeah, if you don't come learn on Duolingo, if you don't come back to Duolingo, then you're not learning.

So we track a lot of this with the work that we do.

We make sure that as we're making changes to the streak, we're not hurting the learning experience and we don't have a ton of interaction with it.

So we're constantly thinking about this.

But thank you, Luis, for saying that.

It makes sense to me.

Okay, so let's get into the motherload of learnings from the journey of streaks.

So the first version went from XP to one lesson.

Talk about the key lessons insights and also wrong turns along the way to what we see today.

Duolingo has a strong test it philosophy.

We're willing to test a lot of different, honestly, we'd much rather test it than debate it for days and days.

So we actually followed up this experiment with, and this is a little bit later with, hey, what if we make it even easier to extend your streak?

And so we actually tested, hey, if you do one exercise, just one exercise in a lesson, we'll extend your streak.

And the insight was good.

You look at the funnel.

Hey, there's a lot of users who are starting but not finishing lessons.

They're not extending your streak.

The loss aversion doesn't kick in.

They don't come back.

So this followed that train of thought.

What we realized when we ran this experiment is DAUs moved not one bit.

And what we were doing by, and if we go back to like unit of measure, we had dumbed down the unit of, and nobody thinks about, I just want to come, you do one question on Duolingo.

Nobody thinks about that.

So we had more like a less clear unit of measure that we were basing our streak around.

And the users that we were capturing with our streak, you come, you do one or two questions on Duolingo, then you leave.

We're like the least engaged users imaginable.

And so I think that's something also to think about as you're building your streak is like, what is the user that you're solving for?

So not only what is the kind of habit that you're building for, but like what is the level of commitment?

That was an example where we over -indexed on a type of user who we honestly just weren't going to keep.

That was a very easy shutdown decision.

That's an awesome story.

Just to comment on that real quick, you went, let's just go to the extreme and make it, just like streaks.

Yeah, get everyone going streaks forever.

And then I love that it turned out and it's not bringing in users that you want and it's dumbing down experience.

It makes me think of FarmVille, where you have to go and harvest your crops every whatever hour and just like that lasts for a bit.

And then eventually people are like, what the hell am I doing with my life?

Yeah, exactly. I mean, and we test every, so we, I was looking at the numbers as well.

We have run in the last four years over 600 experiments on the street.

So every other day, effective 100, we're running an experiment.

And they range from big like this, like changing how the mechanic works to like, let's swap a string with another string and see if that copy is better for users.

So we're constantly testing on everything.

I do think that like, I'd be more careful running that experiment now.

Like at some point, your streak gets big enough that, again, I got 9 million users on the street.

I got to be really careful.

Those are our best retaining users.

You got to be careful.

But in the early days of the streak, I'd say like, test everything.

I mean, see what, don't get super caught up and it has to be like this.

Just test a bunch of stuff and see what speaks most to users.

Because I think, again, you will constantly be surprised by the insights that you get from whether you, we shut down about half of our experiments.

So half of our experiments lose.

We still learn a ton by virtue of running them.

So super, super valuable.

That's actually a good success rate.

A lot of companies have only 20 % of the experiments be positive.

What's your policy on is if it's neutral, do you ship it or do you kill it?

It really depends. If we're adding something and it's neutral, we tend to shut it down because it's just more cognitive load.

It's something that we're going to have to start building around and a UI element that we have to figure out if it's into our system.

I'd say when we do ship a neutral experiment is something that we have real conviction around.

Yeah, maybe this was neutral, but it's going to give us a new platform to then build on top of.

So that experience might be neutral, but now we can build these DAU positive experiments.

And my general take there is though, in that case, build that in as part of your V1 so that you make sure that at least your hypothesis around this roadmap has play should probably be the case.

But in general, shutting down a neutral experiment so you don't introduce more complexity to the app is the way we tend to go.

Makes sense. All right, what else?

What else have you learned along the journey?

Well, maybe I can talk about a few different ways that we structure.

A few different themes that I think we lean on.

So the first is focusing on the zero to seven day user experience.

And I would say this is, if you look at the kind of whatever breakdown of experiments are, we run definitely more than average number of experiments on getting users to go from a zero to seven day streak.

And a lot of this is because we've looked at the data for our retention curves.

And we found is that once you get to seven days, loss aversion kicks in and you retain.

So going from a one to a two day streak, huge jump in retention, two to three day streak, slightly less, but still huge.

It's up until day seven.

Once you hit day seven, it flattens out.

And it's not to say that if you have a 30 day streak, you're way more attentive than day seven, but not in the order of magnitude that it is from day one through seven.

So we do a ton of work to get users to that point where loss aversion kicks in.

And then they don't want to, they don't want to leave the app.

One of the fun ones that we did, and it's honestly as much about process as it is about the feature itself was we have a feature called streak goal.

And it is, again, so much of the stuff seems so obvious in retrospect.

But it was really novel at the time.

We had this idea of like, hey, maybe we'll just goal users to hitting a certain streak length.

As you can imagine, this is pretty powerful user psychology.

And we started with the simplest version of this.

And this is how Duolingo does a lot of our testing.

Rather than design the big complex feature for V1, just do like the simplest encapsulation of what that feature can be.

See if it has legs, and then just add to it iteratively over time.

This is partially how we get to 600 plus experiments on streaks.

They're not all big ones.

But we started, and it was funny, we actually took a learning from our modernization team.

So one of the strings that they had, the pieces of copy that they had worked really, really well was, I think it was your 5 .6 times more likely to finish the course if you subscribed to Plus.

Now it's super, our subscription.

It was a really good hug that if you really cared, you'd sign up.

And so we ran a similar, we had a similar thought where it's like, Oh, let's just tell you how much more likely you are to finish the course if you get a 30 -day streak.

And so we started with that, and I think it was like, you're seven times more likely to finish the course if you have a 30 -day streak.

And just that message when you started a streak, us telling you that was awesome, huge win.

Indicating an outcome.

And Duolingo doesn't have, we have a gem economy, but we don't actually have like, you know, it's just, it's all you learning.

But being able to actually talk about it in terms of the outcomes that a user would think about, in this case, trying to finish the course was a huge win.

So this is where we started and we're like, ah, goal setting.

All right. We should go much harder on that.

Found some thing. And now let's just beat the heck out of it.

So we followed that up with another experiment where we tested different lengths.

So we'll test 14 days and 50 days.

And we found that they were all good, but they appealed to different users.

And so we started to realize, all right, well, we probably need to be more thoughtful about who we give these different options to.

And so then we followed that experiment up with, all right, let's start with 30 days, and then we're going to let you opt out.

You know, we'll say, no, I don't think I can hit it.

And our thinking was, and then if you say no, we'll hit you with an easier goal.

Because we just wanted to get you to commit to a goal.

And this was a fascinating one, because it was a good win to give users that easier goal to try to capture capture them before they said no.

But it was almost just as big a win to add that opt out button.

So we tested separately, and I'm a huge fan of testing, like, way too many arms for an experiment just to, like, be able to isolate your hypotheses.

But but we captured, you know, just what happens if we add an opt out button and adding an opt out button when you would think like, as a PM, oh, I'm like, you know, now users might not engage with my feature, that's a bad thing.

But it was a huge win to let them do that.

And in the learning here was that this intentionality of saying, No, I want it previously was just to continue button.

But now it's like, No, I want to hit 30 days and having that be an intentional decision for them, yes or no, even though again, this had no impact, no, no impact past this screen, everything that I'm talking about now was, you know, just that screen that day and then was all thrown out.

So that optionality was was, was, you know, a huge insight.

And so because of that, we built a goal setting feature where you could choose between different goals, giving users that optionality was, was, likewise, a huge win, I'll say one, one final learning on this.

Again, you talk about like friction and good and bad friction, we thought once we built, you know, a goal picker screen where you could pick between street lengths, we were like, Oh, well, let's like recommend that users do a hard, you know, a harder goal, thinking that okay, well, harder goal is going

to be better retention.

And we'll pre select the harder goal for them.

And this, based on all the learning that I just shared with you, you probably imagine loss pretty significantly, we realized that like, yes, we could speed users through the screen more by virtue of picking a goal for them.

But like, that act of selecting, I think it's 30 days, I think it's 14 days was where we were getting so much of the engagement from this feature.

There's so much human psychology that you all learn through all these experiments of just like how to motivate people with motivates with the motivates.

It was like, you guys should write a book on human psychology and motivation.

I feel very much like a amateur armchair psychologist with everything that at least as far as people who want to learn languages on their phone go right, right, right.

I really understand those folks.

So one, one kind of theme I'm hearing here so far is you guys are basically just like mining for gold, just like looking for like a vein in some mine.

And once you hit it, you're like, Oh, this worked, you just go crazy on just testing all kinds of things to see if you can how far you can take that one little light thread.

Yeah, and I think you know, I shared that that the how this idea came partially from you know, modernization, when that they had I think there's a lot of, you know, because Duolingo runs, you know, I don't know what percentile we're in, but it's got to be a very high percentile of, you know, per capita experiments run

for a company, you know, based on company size, we're just constantly learning so many things.

And there's a really great cross sharing of monetization say, Hey, this thing worked for us.

Is that something you can use?

So I'd say it's rare that we go into something where it's just like, right, let's just let's just try something.

Typically, we have some insight because of all these experiments that we've run that, hey, if we do this, I don't know, it's one year or it's worked here, it's driven this user engagement.

If we, you know, sort of massage that make it, you know, try and this, you know, scenario or like a different screen, you know, we come in, at least with a strong hypothesis of this will work.

A lot of times we do look and we're like, you know, a lot of the apps that we look at actually are games themselves.

So it's like, all right, you're playing Royal match, or, you know, there's a new Pokemon trading card game that I'm spending way too much time on.

You know, you look at these games and see what they're doing.

And it's really good fodder for what we can do.

But a lot of times you're at least going with a strong hypothesis based on what you've seen work elsewhere.

Got it. So just to double down on that point, it's not like just random experiments.

It's here's a hypothesis we were fairly confident, or has a chance to be true.

Let's try it. It's not just yet.

Just try everything.

And I think that like how strongly you feel about the hypothesis directly ties to how hard that experiment is.

Like with copy, for instance, we we've actually set up really good infrastructure for copy testing, and I'm of the opinion that companies should run.

As long as you have the user base to do it like copy test constantly, like the amount of copy test that we've had that is just like, that have one and you I don't know, you just you just try things and you figure out what wins is is definitely legion.

And if ship like massive wins from little copy changes.

Is there an example that just like the impact going back to that goal screen, we used to say continue our like standard CTAs continue.

And we changed that to commit to my goal.

And it was like a massive when even just you know, and again, it was like, okay, users tapping on that, what are we asking them to do commit to the goal?

What is that going to lead them to do commit not you know, churn, just that little copy change that one time right there led to huge wins.

And copy changes are so cheap.

Like it's just you translate us, you know, for us, you know, we have a lot of, you know, users all over the world, the UI languages.

So but like just come up with a bunch of ideas, translate some strings.

This is one where you know, that the feedback that you'll typically get from Luis said so all of our changes at Duolingo go through product review that you know, are reviewed by Luis Luis reviews, every single change that you know, we we propose or every experiment that we run to live copy is just like,

I don't know, test it like there's there's nothing better than be told by Luis, I don't think this is gonna win.

But sure, if you want to, and a lot of times, you know, to his credit, he's right.

And a lot of times, you know, our intuition was right.

But it's just so cheap to do it.

I think when the lift is smaller, it's great to have hypothesis.

But you know, you don't need to beat it up too much.

So on this thread, I didn't realize Luis reviews everything you're planning to change.

And this may be the answer to the question I was going to ask, which is one of the criticisms of running a product and company this way of just experimenting constantly with all these micro improvements and changes is it can lead to something like a monstrosity of a product and experience that isn't

consistent and cohesive.

And just like, that often happens is the solution to that having the founder basically reveal the changes, is there anything else y 'all do to avoid it moving in a becoming farm bill or whatever is a good example?

Yeah, I are product review structure where we've got our head of product design, one of the lead, you know, the product management leaders and then Luis NPR.

And because they see everything it, you know, they have a really high product bar.

And so that helps. I think over time, we just as PMs have to look at, okay, where is our feature headed?

And so, you know, we do this with the streak, at least on a quarterly basis to look at, okay, well, what, what have we learned?

You know, how is our streak developed?

And how do we imagine this going in your future?

I don't think, you know, it's easy to do, you know, and end in some sort of awful local maxima.

If you're not constantly looking at your roadmap and thinking, you know, you don't have a clear strategy, you know, for me, it's like, if you have a clear strategy for where your feature is going, hopefully, all of those A -B tests are not just done, you know, to get some cheap gain, they're done with a long

term goal in mind. I do think though, and we do this every now and then with the streak, eventually, you just hit a local maxima.

And you say, like you talked about lunch and neutral experiments, this is a great example.

It's like, all right, cool.

Now we need to throw a bunch of this stuff out based on all the learnings.

Can we reset this real estate?

Can we reset this UI reset this feature in such a way that is just as good as what we have now, but is way more plain or simple, that we can again, start to layer on those are hard, those are really hard experiments to get win, you know, to win, obviously, because they are so optimized, but they're

really important to do.

Otherwise, yeah, you just end up with a kitchen sink of a feature.

One other tidbit I just want to mention, something that the advantage and advantage y 'all have that other companies don't have is people want to learn like they want to learn the language.

And so getting pushed to come back to an app for something that they want to do is not an advantage a lot of products have.

So anything you want to have there of just like this is why doing go might be a little different from what you're working on.

I mean, that is definitely a benefit if I had an app that this is this is actually why I think a lot of mobile games do streaks differently because, you know, to say that you played a mobile game and somebody who plays a lot of mobile games, you know, that you've done it for 3000 days in a row, like,

I don't know, maybe that hits a little bit different than you've learned Spanish for 3000 days in a row.

I think the comparison set is much larger, though, than a lot of companies give them credit for themselves credit for.

And I think that there's I mean, there's a lot of ways that companies think about their very few companies, I imagine, out there in the world saying, Oh, we don't do some degree of good for our users.

Even if it's like a game, it's like, I don't know, you're like making your giving somebody a moment away from the craziness of their lives.

And so I do think, though, that is contingent on companies who are going to figure out if a streak works for them to figure out how can you frame the streak in such a way that a user does feel good about it.

And it's easier for, you know, do a lingo.

But, you know, I think there's creative ways to phrase this for users.

You know, the other thing, maybe just on that, that I'll say is the streak works really well for do a lingo, because with language learning, it's really hard to see day to day progress and becoming more fluent, like become an influencer is not even the right word, it's like becoming better at Spanish

or whatever. It is a years long process for someone to get better at a language.

I mean, still got to put in thousands of hours if you're going to reach, you know, C1 or C2 fluency.

And that is really hard to track on a day to day.

And so the streak works really well for us because we might not be able to tell you, hey, you now know, 0 .01 % more Spanish, but we can show you, hey, you've gotten your streak a little bit higher.

And so I think this works particularly well when you're an app that is doing something that's going to be sensed or felt over a longer term to help contextualize that progress in a way that makes more sense, or at least feels more tangible to a user.

Great. That was a great context, empowering to a lot of companies that aren't necessarily doing language learning.

Okay, so it took us on a long tangent away from lessons and experiments you ran along the journey of iterating on the streak.

So a few things you've shared so far is just like it started being like started with this XP idea and then went to like a lesson, then you iterated on ways to make it simpler, maybe harder, you added street goals where you commit to like, I'm going to hit a certain goal of streak.

What else? What else have you found that has worked, didn't work, lessons learned.

You know, again, sticking with this one to seven days streak, you know, it is the idea of a streak, particularly probably to this audience is like, obvious, like, Oh, it's a streak.

It, you know, goes, it just counts so many days.

We've realized over time that a lot of users do not understand how a streak works.

And and it can be as big as, you know, as small as well, I don't understand how streak freezes work, or I don't, like my mom the other day was talking to me about she's like, Oh, my I like didn't use dual lingo.

And I come back and I, you know, streak still there.

So like, there's like certain elements of the feature that you know, we can do better at explaining.

But even like, what a streak is, it's it's tracking how many days that I've used the app, yeah, the more that we can make the feature easily comprehensible to users, the more retentive it is in it.

And and we've run a number of experiments to do this, you know, as simple you talked about, you asked about early easy copy changes that we made.

Actually, this is my first win experiment when when I joined dual lingo was, when you start a streak, we use we have little copy at the bottom of the screen that just I don't know, it's kind of like flavor copy, we use it to celebrate you or give you context.

And I ran some tests that just like tried to in eight words, explain what a streak was.

That was it. It was a massive win, because it really required like a really dumbed down here is exactly how the streak worked.

And it really helped users just understand what they needed to do.

And I think this is something that's like you kind of constantly got to remind yourself, particularly if you work in tech and you're building cool tech features, but your user base is not a bunch of tech workers to like think about all right, who is my audience?

And for us, it's not just like tech workers, I people in America, people all over the world of all ages of all cultures.

And so making sure that your your your feature is even something as simple as the street because understandable is critical.

What was the actual copy?

Do you remember it was still I think it's still in the app, like start a day to extend your streak, but miss a day and it resets something like that makes sense to me.

Very clear. Yeah, words.

I love that. Okay. And then when you say massive win, by the way, just to give people a reference point.

What do you what does that look like?

What does a massive win in this scale?

Well, and it's funny, I mean, this was and this was four years ago, but I think it was like in the order of magnitude of over 10 ,000 da use for us.

And actually, maybe this small bit of context, so Duolingo really cares about the metric cur current user retention rate.

And actually, our first ever Duolingo post with Lenny was the newsletter that our former head of product wrote Jorge still the single most popular newsletter post of all time in my newsletter across 300 would highly recommend that if you are interested in this, give it a read.

You know, to summarize, basically, what we found is that if you wanted to drive da use and Duolingo cares, you know, our growth North Star is da use the metrics that is most effective, you know, a percentage change that metric is most effective at driving da use is current user retention rate.

And this is just users who are not new or resurrected, getting them to come back tomorrow.

And so most of the work that our teams do, our retention based teams do is focused on cur.

And so the retention team that I lead focused on cur just so happens to streak is the best feature at driving cur.

And so this was this experiment was the biggest cur when that we had had, I was like a top three cur when anyway for us just this little copy, right?

And as I say, like death copy 1000 different ways sometimes it's not the big beautiful feature, you know, that's going to drive the huge gains, huge gains sometimes it's just something simple as a few words.

I love this. Okay, so when you said 10 ,000 days, I think that references you guys measure incremental impact and absolute numbers of new daily users, you're going to drive with attributed to that experiment.

So yeah, and we do both.

I mean, we'll also look at like a lot of times I'll look at, you know, for retention day one versus day seven versus day 14.

A lot of what I'm looking for is for us to have a better day 14.

Excuse me, better day 14 impact and better day day one impact because it means that users are retaining better over time.

This is particularly for users that would see a future multiple times.

I just like absolute da you numbers because as long as you're controlling for, you know, different biases, like a recency bias, or a novelty bias, it's a really easy way to just have an absolute comparison.

You know, you start to look at percentage changes, and then it's influenced by your treatment, you know, how many users saw the experiment.

But at least you know, an absolute number is is easier in my mind to start compare again, there are doubt, you know, there are pitfalls with it.

But we find that that's pretty useful way that lesson comes up a lot on this podcast and that approach to experiment.

So yeah, you're good, you're in good company.

Quick tangent. If there's not an answer to this, no problem.

Coming back to the idea of just like experimenting like crazy and not creating a product that nobody wants to use anymore long term.

Is there an example of an experiment that was positive that you all decided no, we don't actually think this is what we want in the product, they ended up not shipping.

You know, retention doesn't only work on the streak, although, you know, you would you would think we did most of our work is the streak.

We've touched a lot of different surfaces over the years.

And there was one experiment that we launched that, you know, we talked about XP earlier.

In the lesson, the only UI elements are a progress bar at the top, and then how many hearts you have, right.

So we keep it really simple.

And this very much speaks to the design, you know, philosophy of Duolingo, which is simpler, UI is better.

And we decided, hey, let's add XP in there.

And so let's show your XP ticking up as you're going, you know, through a lesson that's going to make the user feel good, it's going to give you know, show you what you've earned, you're gonna be less likely to quit all of these good reasons to do it.

And then you finish the lesson and then we'll show you've collected all this XP.

And at one, I mean, the hypothesis was a good one.

But we realized and I remember having this conversation with Luis is like, cool, this is our most important screen in the app.

It is our lesson is where users learn and the focus here is on learning.

And now you've added this other thing up there to distract, you know, that could be distracting for users.

And I think the question you know, we talked about roadmaps and strategy here, the question that he had for me, and I didn't have a good answer for at the time was like, so what else are you gonna do with us?

Like, what's your iteration ideas?

Where's this going to go?

Is this going to make the lesson experience more gamified or and what we realized is that like, honestly, it was kind of just a, you know, an easy engagement when idea but we had touched our most, you know, sacred space in the app to do that.

And so that was a case where it's like, yeah, it was a nice win.

But we'd added that UI element.

And, you know, at least at the time, it was less clear what we would do with it.

And we realized that like, long term, it was just going to get in the way.

And we'd rather for simplicity sake, pause that, you know, shut it down and keep the lesson, you know, to be the a little bit of learning sanctuary it was.

Now, it's funny. Nowadays, I think we actually have enough XP based mechanics and fun things that we can do that, like, I think actually a lot of our, you know, the beliefs about the lesson experience have changed, such as something like that could work.

But at the time, you know, didn't feel good to keep that around.

That was an awesome example.

Hopefully, we have time to talk about how the team operates, where my mind goes as like, Oh, but do you have all these PMs and teams that want to show impact and the performance reviews and all that stuff?

And you're shipping, so you're not shipping something they're like, Oh, look, we did a win.

So I want to chat about that later.

But let's keep going on things you've learned and things that didn't work on the journey.

The the other thing that I'll call out with the the streak is, you know, it's like we have the the image of the streak is this flame, right.

And you know, we have the streak flame, and it's very much quarter iconography.

It's important to acknowledge that that's a metaphor for a retention mechanic, like the idea of keeping a flame lit.

And again, if you've, I think we've we've established the flame as you know, for a lot of users as sort of their understanding of a streak, which is great.

But there's a lot of people, you know, in different cultural context and different, you know, stages of life where the idea of like keeping a flame lit to show your commitment to something makes less sense.

We did some UXR in India many years ago, and this was something that just like did not resonate at all there, which was which was a really interesting learning.

And that's something it's like, again, depending upon what your user base is, like, the more global UXR you can do to understand how users are actually understanding and experience your feature the better because you just, again, encounter insights like this.

And so even our screen design, you know, we used to have a flame, it was just it was mostly this flame that would like light up every day.

But again, it was like an indication of a metaphor for a mechanic.

And when we redesigned it, we did this Kurt are one of our animators did this awesome odometer animation where it's like your number would tick every day, it like kind of like look good.

But from a product perspective, what was cool is we actually focused the design on the screen to show your number going up.

And then it would say, you know, like seven day streak eight day streak.

And I think that as you're thinking about designing around a streak, don't get too bought up, you know, or caught up into like, what is this, you know, like the beautiful story that you're trying to tell at the expense of it being a really comprehensible feature.

And so as you're thinking about product design, making that product design a clear distillation of this is what we're actually tracking, you know, form should follow a function here, you know, was a was it was a learning for us.

And you'll see that now in a lot of places where we're showing streak, we're really leading with the number, not necessarily the flame.

That's that's a theme that I'm hearing again and again is clarity.

Don't obsess with making it too felt like clever.

And don't ever think it just like clarity has a big impact.

clarity also doesn't have to come at the expense of delight.

And this is something where, you know, you hit a milestone and duo gets the you know, it becomes we call him a Phoenix duo, and he becomes awesome.

And you know, lights on fire.

And I think there are things that you can do to still make the experience really exciting and delightful and celebratory and and I would I would not lose that but just don't do it at the expense.

And I think it's also about figuring out for what you know, you can get away with doing more of this for users who are deeper into their streak experience than users who are starting where it's like your goal for the one day streak users just to make sure do they understand how this feature works?

I mean, even something again, just like another random experiment, at the bottom of the streak screen with a calendar.

And over the years, it just looks more and more calendar like and that is simply because we find that the more we make it look like a calendar days on top, you know, little circles, the check like more we make it look like calendar, the more that people realize, hey, this is a day a daily mechanic.

And so think about the screen holistically, but every single thing that you're doing on the screen, how can you use it to communicate?

What is the point of this feature?

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I imagine one of the biggest wins was just giving people flexibility along the journey like streak freezes and all these things.

Is that a big vein of opportunity discovery?

It is it is great. Actually, I'm going to show you the one of the most thoughtful gifts that anybody has ever given to me.

This is our Duolingo Serenity or Streak Serenity prayer.

My co -leader, Antonio.

It's like it is right.

It's like for me. It's amazing.

And so it says, Luis grant me the serenity to accept the flexibility I need, the courage to reach perfection when I can and the wisdom to celebrate regardless.

And that actually is like kind of our strategy with the streaks of the show and tell by the way, that was great.

Yeah, I will. Well, I guess for, you know, podcast listeners who have to get an image somewhere.

The this idea of like flexibility versus perfection.

And then regardless celebration is core to how we think about the streak because, you know, I think for the streak for us, it's very much a bend not break.

You know, you're going to miss a day.

I'd rather you come back, you know, having not, you know, having missed that day to an intact streak.

But if you don't have to miss a day, much rather you don't and much rather you come back and use the app every day.

So that that thing on flexibility, though, that's almost certainly been the biggest, you know, from a mechanic perspective, the biggest DAU driver, you know, one of the earliest experiments we ran was going from used to only be able to have one streak freeze.

And then we let you have either two or three.

So we tested two different arms.

It was an again, another huge DAU when this actually is funny, it was something that this is again, kind of a call back to that growth model post from from Jorge.

It actually was really bad for Kerr, because we were basically saying, Hey, you can take a day off, you know, that's okay.

But it was really good for this is going to be like alphabet soup, I war an active weekly active user retention return rate.

So basically, users who had taken a day off, we were getting them to come back more at higher rates.

And so it made up for our losses and Kerr, but effectively, what this meant is that, you know, why to streak freezes work better than one was, I don't know, sometimes people just need a lot more flexibility than one day.

But one of the again, the really interesting inside of this experiment was that three streak freezes was actually no better than two streak freezes.

And there were two competing things here.

And I think this is important if you're going to build a streak, you know, to figure out what your flexibility mechanic is, we are getting more users to return after longer times away to an intact, you know, to an intact streak.

But if you start taking three days off from any habit, it's just going to be less likely that you return even four days later.

And so we had these competing things where users might more users might be returning to a streak, but a lot of users were also just not coming back, we were training them to, you know, take more time off.

So that flexibility, what's the right amount of flow?

I mean, we've again, this is another area, we've run hundreds of experiments on what is the right number of flexibility, what is the right amount of flexibility?

And we, we are constantly surprised here, we don't, I still don't have the answer for at every point in your streak journey, how much flexibility you need.

One thing that I can say with certainty, though, is, give more flexibility when a user is starting their streak.

Again, one of our biggest streak freeze experiment when I feel like I'm constantly saying this one of our biggest wins, but they all were really, really big.

One of our biggest streak freeze wins was when you start a new streak, we give you two streak freezes.

And again, it's so funny to think back, it's like, how are we not doing this to begin with, but at the time, the streak freezes kind of an overly gamified mechanic, you had to buy them with gems, that's our in app currency, you know, because we wanted the whole idea of, you know, this to feel like you,

like it was really, you know, something you earned that, you know, there was a little bit of pain to getting that streak freeze.

And so we tested, though, what if we just give users when they start off their streak to streak, streak freezes, and holy smokes to that win, and sort of obvious now, you know, in retrospect, but if you have a one or a two or a three day streak, it's really easy just to let it die.

And restart, you know, again, you need to get to seven days, what we've seen in the data for it to really lock in.

And so giving users more flexibility, so it's harder to lose their streak initially.

And then conversely, and this is what we keep learning.

Eventually, once people get on long streaks, you kind of don't want to give them as much flexibility, you know, because there's a lot of times where yeah, users don't add I'm like this, I've got like a 400 day streak note that that is a lot less time than I've been at Duolingo, I have lost and restarted

streaks a lot of times of my time at Duolingo.

But you start getting a lot of streaks.

And you really care about this feature, you really care about your streak.

And most people, as long as you're not like backpacking through, I don't know, you know, the backcountry of Utah, you know, you'll be in a place where you can get service.

And so figuring out where is the you know, who is the user that actually could use Duolingo and not conditioning them to start taking days off that they didn't otherwise need to do is is important to figure out sort of where that line is for your feature.

This is fascinating.

You can also buy a streak right?

Like with money is that that's a feature right?

Yeah, you can. It's funny, this is this is also something that we buy.

Yeah, you can buy a freezer or free.

Sorry, not a street.

Yes, you can you can buy a streak freeze in the way it works is you can buy gems, and then you can use those gems to buy a streak.

And this is something we wrestle with.

We're actively working on experiment right now that's having a small hit revenue.

But it's a really nice one for attention.

And I think it's actually worth thinking about from day one, as you're building a streak, do you see this more as a monetization feature?

And do you see this more as a retention feature?

What's the role of monetization in this?

What's the role of retention?

And I think, for us, it started out much more organically.

And so we have a lot of monetization hooks that again, as the retention PM, I would love to get rid of.

But again, it's sort of part of how the streak works right now.

And so we always have this tension of, hey, if we start to make it harder to buy streak freezes, then fewer people buy them, you know, buy gems to buy them.

And so there's this more convoluted, you know, series of impacts that happen.

Yeah, I love that. I love that people wanting to buy streak freezes, like the ultimate sign of how much streaks matter.

Yeah, it's streak, streak freezes.

The other big one that we've, that we've recently demonetized or introduced a free option for is getting back a lost streak.

So you start losing streak, we had a feature in the day, you know, back in the day called streak repair, we give you your streak back, you had to pay gems.

But we found that worked way better was a feature called earnback.

And this is basically where you would have to do a certain number of lessons as long as you came back within, you know, a window soon after losing your streak, do a few lessons, we just give you your streak back.

And it was such a retention winner.

And again, what we thought about was, it feels like you've earned it so much more when you've done like you deserve to have your streak back, we haven't cheapened the streak.

Because you've done something and in this sense, this idea of cheapening the streak is something like from a philosophical philosophy of the street.

From a philosophical level, we wrestle with all the time of cool, we're giving out more streak freezes.

At what point do we cross the line and users start to realize their streak means nothing?

Now, everything that we've seen users are totally cool with using streak freezes and still thinking about the streak is this meaningful thing.

But my colleague, Antonia, who made that awesome cross stitch for me, she is sort of the keeper for us of the sanctity of the streak.

And a lot of times as we and I think this is this is really important to have as you're thinking about building your streak, you can almost always get engagement wins up to a certain point by just cheapening the streak, making it easier to extend, letting users have more flexibility.

But you kind of got to hold the line at some point, it's not clear where that line is.

And once you talk about one way doors or two way doors, there's a point where you go too far, and it's a one way door.

And all of a sudden, those users, those 9 million users on one year streaks don't care about the streak anymore.

And that is, I don't know, again, retention PM perspective, that'd be an extinction level event for us.

I don't want all of these users to stop caring about their streak.

And so to have somebody who is invested in the sanctity of the streak, and for us, it's Antonia and Louise, he's very good about this, is really important just so you make sure you don't go too far.

That's an awesome insight.

And person notifications, I think are another example, this in general for companies, like how much is too much, because everyone's just like, let's just send another push, it's fine, just one more.

And so your solution to that is a person is like the keeper and the gate, almost the gatekeeper, plus the founder of how far is too far.

It's good if you can have that.

I think push notifications are also easier, because, you know, there's a lot of things you can do around, all right, we'll set a budget cap for how many notifications we'll send, you know, you can create a policy.

Yeah, policies. But I think with a lot of things, it's hard, at least for the streak, it's harder to create policies for in the same way, a lot of it has to be done based on feel.

And so you kind of just got to use your best judgment at times.

Sweet. Okay, any other maybe like one or two more lessons from this journey of what streaks has become today?

I mean, I can you mentioned notifications, I've mentioned this a few times.

What it's funny, you tend to think of like exactly as you say, you can just always send another notification, it's going to be some win.

And at some point, you know, it'll be a bad experience.

But it's tough to see that there's actually a notification that we so we send two notifications related to your core streak each day.

The first is a practice reminder, we send it this is actually an interesting insight 23 and a half hours after you practice the day before.

Whoa, that is a three and a half.

Okay, so basically, if you practice at noon today, we'll send to you at 1130am tomorrow.

And we have done it because it's like assuming they are free in that time the day they'll be free the same time.

And we actually moved we used to let users set this practice reminder time and you know, our thinking was cool, you're going to say 7pm.

That's when I really want to extend my streak each day.

And then you know what, I said this is somebody with two kids life gets in the way life always gets in the way and when you think you're going to practice will change your life will change whatever.

And what we realized is the best indicator of when you should practice was when did you practice the day before we could almost certainly get more detailed we have tried a bunch of ways to have much more complex logic and what always wins is 23 and a half hours.

So just like reveal behavior versus Yeah, exactly.

So so we again, we send this practice reminder 23 and a half hours later, the other thing that we'll do though is we'll send it what we call a streak saver.

And this is at 10 o 'clock at night, if you have not extended your streak, we'll send you a message saying, Hey, you know, like it's it's your last chance this is this is it if you don't extend your streak and you would think that like, that's kind of spammy.

That's that's kind of annoying to get a notification from an app at 10pm.

But what we found is because people care about their streak, their streak is this good thing that they attach positive emotions they don't really want to lose that notification reminding them, Hey, come back and like people see this by and large as a positive notification and on a negative notification,

obviously, it serves our purposes as well of getting users to come back and not lose their streaks.

But again, I think if you can think about your notification strategy related to what is the feature that it's tied to how do users perceive that you can almost certainly get a not get away with more, but you know, you can be thoughtful about notification load, and when to send notifications.

And again, for us this like late night message that's also highly impactful, super good, you know, is actually something that could be perceived as spammy.

But a lot of our users really do like somebody who it's often late at night to come and I work here and I'm like, Oh, forgot to do my do you know, I was thinking about Duolingo all day, you know, here it is 1115.

And I saw it down at that message is really powerful.

Yeah. And it saved me many times.

I totally know that message.

And I love that it's like a late night message from an app.

Very rarely do you actually are happy about that.

And I love that this actually is a good example where like, it's really, it's really funny all of the stories that you hear about people extending their street, you know, if you look around a Duolingo party, you know, we're in it's like 10 1130 1145, all the Duolingo employees that are like doing their

lesson at the last minute.

You always see these like pictures of people in the club doing or like at a concert doing Duolingo.

And yeah, because it's like otherwise that you're gonna use a streak freezer.

God forbid, you will lose your streak.

And so funny. Okay, anything else?

And if there's like more than one more, definitely share but any other really interesting lessons or wrong turns or insights.

You know, I talked about streak freezes, and we've done a lot with streak freeze.

But I think if you're going to make flexibility a thing, it's probably also useful thinking about how do you celebrate perfection.

And so we have a feature that we have, it is the simplest thing in the world.

It's called perfect streak.

And it's just if you don't use a streak freeze for a few days, we make your streak look gold, and we make your little progress bar on the calendar, just look a little bit nicer, there's no reward for doing it, you don't get anything other than this nice little indication.

And it is awesome. It is, it is a simple feature.

It is ultra not complex.

And it is really powerful not only for getting users to, you know, as a bit of a reward to be hey, you know, get to seven days, you know, without using a streak freeze, and you know, your streak becomes perfect.

But it's also a really nice indication of users who aren't using streak freezes.

Here's the thing that if you, you know, if you don't use a streak freeze, which again, Candelay, I would love for you never to use a streak freeze, if you don't use a streak freeze, your streak will stay, you know, perfect.

It's funny, we actually just, you know, we're constantly, you know, responding to bug reports about the streak, you know, it is, I swear to God, we have that we have the best infrastructure around this feature because it is important.

We had an employee who lost her like a four month perfect streak.

And, you know, it was a big deal for her because she, you know, because she like did her lesson as she was crossing international dateline, there was like a bunch of stuff going on that was like, it was just kind of weird in her back end.

But like, people start to care about perfection as much as they do their streak.

And you know, for that person, it was it was a big deal when they lost their perfect streak.

And so, you know, this is just an example of like, if you're gonna, if you're gonna go after flexibility, which is good finding a way to pull users back into perfection, is a really important counterweight to have.

What I'm imagining is you guys need like a Amazon style chat bot that just gives you the streak back just like, okay, here we go.

We have very much so we have if people lose their streak, you know, there's ways to get in contact with us.

But we've actually thought about that where it's like, okay, we should just like build a self service feature.

And if you're, if we think that your excuse is good enough, whatever, we'll just yeah, yeah, because again, it's for us to ship it back.

I'm much rather you be on, you know, beyond a streak than you know, have lost it particularly if right.

But it also can feel that easy.

I love this. I also love this point about just the power of the animation and user experience having impact that's really interesting.

Is that something you find often just like make like celebrating and making it feel really amazing without like copy or you know, or like any features just like holy, you're awesome.

This is another thing where it's like, when users care about the feature using not only animation haptics sound effects using and it's funny, we don't have sound effects on the streak.

There's probably something we'll look at in the not too distant future.

But like haptics are like something we have done a lot of testing on like the phone vibrating.

Yeah, exactly. It's fallen, you know, like there being a really cool haptic pattern as you extend your streak.

All of this stuff wins.

And it's cool because I think it there's a few reasons.

One is it just makes you feel good, right?

You know, you you get some cool moment your streak and and we celebrate you and we celebrate you in this visual way and your phone's buzz and it just like feels awesome.

The other thing it does is it like causes you to pause on that screen.

And I think there's this desire as you think through a lot of you know, as PMs think through like, Oh, how can I get users through this funnel as painlessly as possible?

And I talked about good fortune early.

There's a lot of times where I don't, I want you to stop, want you to stop and like land on this screen.

You got to be careful not to do this for too many screens, right?

But like, for the one big ones, sometimes I just want you to pause there and enjoy the moment.

Because if I can get you to enjoy the moment more, you're going to care more about your streak and you're going to be coming back tomorrow.

And so animations that are cool, and that cause you to like really soak it in haptics, you know, that feel good, all of that comes together to make you really focus on that moment.

All of that just gets users more connected to their streak.

So animation in the right times works well.

And it's something we've had win quite a lot.

Who designs the haptics stuff?

Is there like a haptic designer?

For the longest time, it would be a product designer, or it initially started as like the engineer would be like, Alright, you know, we'd cobble together haptics based on what they felt good, then it became a product design role where they would kind of use their best judgment.

We actually just recently required an animation studio, Hobbs in Detroit.

And now they are the sort of keepers of, you know, they're do a lot of motion design work haptics very close to that.

And so they do a lot of that.

I do remember trying to hire for a while a haptics like contractor, like haptics design.

And it was the saddest hiring I've ever done.

Because it's just like, I don't know, like, it was such a specific, like, I just went through a lot of people who, you know, it's just a really tricky space of like, kind of sound effects, kind of motion design, sort of technical, not a unique role, very unique, specific skill set, right?

And there's very few apps that really need this deeply.

So you're almost creating this person.

Yeah. That is fascinating.

I don't want I'm gonna that's like a whole podcast on its own.

By the way, I was gonna say as you're talking about this, I love that.

It's a win to celebrate people that don't lose their streak, like you introduced this way to make it flexible.

And that's a big win.

And then you could go the opposite direction of if you don't use this feature, you also feel even better.

Well, and it's funny, you, like you talked about the danger of feature bloat, we sort of talked about the danger of feature bloat.

This is actually something I'm constantly thinking about with this.

Like we have the streak, but then we also have the perfect streak.

And we can count how many we count how many weeks you've had a perfect streak.

All of a sudden, we have two streak numbers that are kind of competing with each other.

It's funny, we actually don't introduce the concept of a perfect streak until after you've hit seven days.

And some of this is just because the cognitive load of additional streak features, a lot of our like cooler streak features, you got to get on a long enough streak.

And not to say we haven't tested it, because we have because we've done everything.

Introducing these features earlier, but what we found is that pretty universally they lose when we introduce too many things, too many concepts to users too early in Okay, sweet.

I know that we can go down this track for hours and hours, there's endless learnings about all the things you all have done along the journey.

I'm going to shift to talking about how your team operates.

So there's a lot of threads you touched on of just how a team can do this so well ship 600 experiments, as you said, continue to find opportunity.

What are some maybe lessons or advice you'd have for folks that are like, oh, wow, I want to work more like this from your team's experience.

How does your team operate that folks can learn?

Yeah, maybe just a little bit of context, we're dueling go cares a lot about metrics.

So most of our teams are metric based teams.

So we do the most work with streak.

But, you know, are the metric what we really care about at the end of the day is cur and and da us because we see that da use hit cur and so when you can be really laser focused on my goal each quarter is to make this metric go up, I think it's much easier to make sure that you're working on the highest

ROI thing, I think when you think more about like, oh, I want to make this feature better, I think it's easier to get lost in what better means and how you think about better.

And so I do think that like having a really strong degree of focus, you know, as a team on, you know, what is the metric that I'm caring about and how is that directing my efforts is versus feature oriented.

So basically, your teams are structured around a metric slash a goal slash outcome versus we own this feature.

So we retention owns streak, I guess, but that's only because we've seen streak drive cur better than any feature.

But we are not I mean, we have this, you know, IAP hook with our streak freeze purchases, there are other teams that work on you know, that can and have worked on the streak because it's not ours to say no, no, we do all the iterations here.

We just know that it drives our metric better in the same way that like leaderboards.

You know, we have a team that focuses on how much time you spent we want users spend more time on Duolingo, so they're learning more leaderboards is the best vector for doing.

And so that team does a lot of leaderboards work.

But every now and then I have an idea that I think we highly retentive and I will go in and pitch to them and then we'll do some change the leaderboard to make it more attentive.

And so but I but I do think having that clear metric of we're trying to drive cur not we're trying to just make this feature better helps at least make sure that you know, give the team clear marching orders and that focus I think is really good for prioritizing backlog.

Cool. This is a really important point.

This is the same way Airbnb worked when I worked there for a long time is it's here's a goal that we want your team to be responsible for.

You could work on any product you need to hit this goal.

As you said, often, like various products are most connected to what you're doing.

But what you're describing is like, even though it seems kind of like I imagine you own it from a bug perspective, and you're kind of like are the shepherd of this part of the feature because it hits your goal helps your girl most but any other team can come in and be like, Jackson, we need to work

on some streak stuff to help with learning.

You're like, go for it.

Does that just a tangent there?

Do they like work really closely with your team if they want to do some work in the code?

Is it like how does that work?

Yeah, if if you're again, this is where I say they're soft ownership, we're not against teams doing things to the streak, but if we're going to do something, given you know, we probably have multiple quarters worth of a roadmap around the stress, they probably we do multiple quarters of roadmap for what we

can do to the streak.

If other teams want to come and mess with it, okay, we got to just figure out how is that going to work with you know, what what our plans for the streak were?

How do we make sure a lot of times when teams are coming in thinking, Hey, let's do this to the streak, they're like in context that we might have.

And so there's as much of like a much simpler version of what we're doing now a bit of a knowledge sharing of saying, All right, well, this is what we think about the streak, this is what we've seen work hasn't worked.

How does that influence some of the hypothesis that you have?

And so I think getting that really making sure the juice is worth the squeeze.

Good old fashioned product management work right there.

Cool. What else is interesting about how you all operate and how you'll work to achieve the sort of success?

Again, my team lead runs is the Antonia runs like the most effective, you know, really process if you're going to run this many experience, you have to be really process oriented and really thoughtful about which experiments am I going to run when how is that going to set up the next one we you know,

there's there's heavy Jira automation, I think sometimes the Atlassian suite makes my eyes bleed.

But like there's a lot of times where that degree of process helps the team on block engineers and make them move really fast.

And so making sure that you have really good process around how are you going to run so many experiments, it's, you know, it's it's worth investing in.

Can you follow that thread?

Actually, just what do you when you say that?

What does that look like?

What are some elements of that process to make this work efficiently, all the way down to really detailed roadmaps around all right, we're running this experiment is based on the results of this experiment or might, you know, hook into an element of this feature, how do we make sure that we're lining

up implementation on this so that as soon as this thing runs, and we're ready to go, we can start rolling out the next one, you know, I hate features just sitting around at us not again, continuing that thread.

So it's not just thinking about what's our engineering bandwidth, but also what's the design bandwidth to make sure that we have the next iteration of this feature ready to go.

You know, we're planning months out as we think about these feature iterations, even small ones, you know, feature iterations, because again, you just you lose when you lose cycles, you know, not pushing on a feature, it's just sort of lost opportunity.

And so everything from manage, you know, being thoughtful about engineering roadmaps to design roadmaps to product roadmaps, all of that needs to come together in a system.

So essentially mapping dependencies across function.

And you're saying in Jira, you can do this, you can do a lot of in Jira, there's a there is a non zero amount of Google Docs that we have that sometimes does things.

Yep, a little bit. I don't know.

Sometimes it just looks a little bit nicer.

It's a little more helpful.

But Jira is our it is where the motherlode of process is.

Great. Okay, what else?

Another thing that I'll just say is like, we really resist the urge to do the big v one.

And I think this is, you know, I shared the street goal example, where a lot of times when we're exploring something, we will say, Okay, well, like, that's cool.

How do we strip away a bunch of stuff and figure out what our core hypothesis is, and then just ship that thing first as a v one, because it's easy.

And I found this time and time again, it's easy to add things to features that make them win.

Like, I've worked in retention engagement long enough, I can like, add enough like things to pull and bells to add and whistles and the you know, to make something win.

But you know, there's a lot of times where it's like, cool, well, they don't want because all the whistles you added, not because of what your core hypothesis was.

And a lot of times, if you can just really simplify what the feature is, it's also much easier to ship, it's easier to design, you're not designing for a whole system, you're designing for, you know, something something much simpler.

And so getting everybody to think that way, ends up allow, you know, allows us to end up shipping faster, shipping, simpler, you know, designing faster, getting faster approval, getting insight, and then doing what I talked about with street goal, being able to run iteration after iteration after iteration,

add these things iteratively.

And then, now you not only by doing this, are you able to move faster, but you get confidence at each step of the way that, hey, my series of my hypotheses, you know, is actually born out, or if it's not, cool, then we're going to drop that part of the feature and then just ship what actually matters.

If I can try to summarize kind of the broad lesson so far that I'm hearing, and maybe you would have shared this, but I'm just thinking like, if I were to try to design a company to operate that we operate, you essentially map all the levers that drive the business.

So you have kind of this mapping of all the metrics that drive up to growth and, and daily active users, you ended up being the biggest specific metric to move to drive growth long term.

So there's like, imagine a tree of all the opportunities you could work on, you found like, this is what is most connected to our growth long term, you basically just start mining, I don't know if mining is the right metaphor, but just like looking for things that move that specific metric, you just

like, look and poke and explore.

And then once you find one, you just go real deep on trying a lot of different you can come up with a hypothesis and a strategy of here is how we think we can do this, and how we can move this and then you just try a bunch of stuff.

There's also this element of the rest of development quote, there's always money in the banana stand comes to mind, where it's just like, keep working on see, there's more, there's going to be more opportunity.

And this, yeah, when I joined Duolingo, the PM that I took over for Anton, who used to lead the retention team, I remember saying, dude, the streak like, it just counts up, you guys have been tested on for years, how much more work can we do on the streak?

And he was like, Jackson, you child, you didn't say exactly this, but this is how I felt it like Jackson, you child, there is so we're not even 30 % of the way optimized.

And four years later, I say that with like such conviction, we are so far away from what I mean, we've made a ton of strides, but we are still so far away.

And every quarter where we ship a ton of wins and improvements to the streak, it just continues to prove to me that like, there is so much more to be done.

So I think your framing of it is, and I would say there's a lot of thought that goes into, again, I talked about the strength of the hypothesis that you have, you have to have as you start to build out larger future strategy, I do think it's really important to not just do a bunch of random stuff, but do

it with intent, you know, with a goal in mind.

Otherwise, you do end up in these local, you know, local maximas.

But yeah, I mean, there's still a bunch of stuff that we haven't tried that, you know, I think we have high confidence in, you know, working out and so we'll, we'll keep doing that.

Are there any other say lasting lessons from this journey that if someone were to try to operate this way, build streaks into their product, anything you'd recommend?

Yeah, I really do think it starts with, you know, it streaks are an engagement hack.

You know, you can you can make your app more retentive, I'm almost positive, almost every app out there can make it more attentive.

It is loss aversion.

That is, you know, again, armchair psychologist Jackson, like, it's just a human thing that works on humans.

But if your if your app is not something that users want to use every day or whatever, you know, cadence you want your app to be, you know, to work on, it's going to be, you're only going to get so much from that streak.

And honestly, it's probably going to distract you from what really should matter, which is making your app something that people want to use every day.

And so if you start focusing on the streak, but you haven't made that enjoyable experiment experience, you're just going to waste a lot of time, honestly.

And so I think making sure that you have your core loop of your app figured out that that it is giving value to users is something that they want to come back to every day.

That really sets the stage for something to layer a streak on.

So resist the temptation if you haven't, you know, if you don't think you've reached that point to go too hard down the you know, the path of streak.

That's a really good point.

Just like a streak is not going to solve your problems if people don't actually care about the core value you're providing.

No, and honestly, it'll probably cause more problems.

If what you end up focusing on is how do I make the street highly engaging, but your app isn't I mean, you're just you're you're you're wasting time that could otherwise be, you know, better spent on solving more or critical problems.

So that's that's one learning.

You know, the other thing that I'll say is, and we met with one of our board members, Bing, Bing Gordon a few weeks or a few months ago, rather.

And he had this comment where he was just like, The reason why users care about your streak so much is because you care about your streaks much you being Duolingo, like the reason why users care about our streak so much because Duolingo cares about the streaks, much more like, what do you mean, what is like,

well, after every session, you see a big streak screen, and it's animated cooler than almost any other screen in the app.

And then sometimes you see some other screens, and there's all these other feet, like, you don't let a user forget it, you talk about them and messages.

And, and so I think it's worth thinking about, look, if you're going to build a streak, and then you're going to seconded off into the corner of your app, you know, where users aren't going to see it, like, they're probably not going to care about it as much.

And which might be fine, because there might be other levers that you think are more important to pull on.

But there's a reason why, you know, we focus as much on the streak, you know, as we do, and that's because we want it to be top of mind for for users.

And it's not by accident, then that users start to care about it.

And so I think just as you're thinking about building the streak, making sure that you're giving it the visibility it deserves, if you want it to have the kind of impact that Duolingo has, you know, it's sort of an important hierarchy principle to think about as you design things.

That's such a good point.

Like you look for cues to the app of tell me what I should pay attention to what's important if you're just like fire explosions, you hit a streak, oh, maybe I should pay attention to this feature.

And then the push notifications obviously encourage you there too.

Anything else along those lines?

Maybe final thing is, look, we ran so many tests on our Duolingo streak to figure out what work.

I mean, we have a philosophy of Duolingo of tests at first, you know, we are a lot of times willing to test things.

I really think that if you're gonna try to introduce a streak, or you want to improve on the streak you have, like, don't get too caught up in the philosophy of everything.

I mean, make sure your hypotheses feel like they're good, but my recommendation is just try things.

And this is again, you said it earlier, it's like, this is as much human psychology as anything.

And as soon as that becomes the case, you kind of just got to understand what users respond to.

And the easiest way to do that is to stop spending time batting around ideas in a conference room and just try some stuff.

So huge recommendation to if you're gonna invest in a streak, try and figure out what works through testing with users rather than trying to get it perfect on the first try.

Say someone's listening, they're like, should we do streak?

Because it's worth doing.

What's your take on just like the chances that a streak feature would be helpful to another consumer?

I am well known for saying in the company that I think every streak, every team, every app could benefit from a streak.

Now how you implement it is very different.

And I think you gotta like, what is your users use case?

Like, if they're going to come use, I don't know, tax software.

Okay, you know, not only say this tax software to be a hard one, but maybe it's all about, you know, you need users to come back every day during the tax season, or how many times I don't know, you know, now that I say this out loud times you upload your, yeah, that is a hard use case.

But the vast majority of companies, I think have a good idea of like, all right, here is my ideal use case, I want users to come here, three times a month, that would be ideal, you know, are four times a month, you can build a streak to work.

I mean, Peloton has weekly streaks, because the idea of doing a Peloton, you know, workout every single day is hard for a lot of, was hard for this user during COVID, you know, it's just like, every now and then you get on the Peloton, that was great.

But the idea of a weekly streak was something that I could keep up.

And so I think figure out what your usage pattern is, as a user, and then build your streak around it.

But, you know, as long as you're not, you know, like a really, again, the tax example is probably a good counterfactual.

But as long as you have some degree of frequency in your, in your use, I think almost anything can have a, can have a streak.

So Duolingo, it's again, a $14 billion company, this feature, possibly the most contributing factor other than the core, you know, product to that level of success and market cap.

And it's hard to imagine another just feature of a product that has had this much impact on, on growth and revenue and building this sort of business.

So I love that we spent this much time on it, the mother load, the mother load of advice and insights.

So thank you again for putting it.

Very fun. With that, we've reached our very exciting lightning round.

Are you ready? I'm ready.

First question, what are two or three books you recommended most to other people?

All right. I'll start with a guide to Midwest conversation.

So I'm based in Kansas City.

I'm a proud Midwesterner.

And us Midwesterners talk in a certain way.

I think, you know, you hear about Minnesota Nice.

But we tend not to say what we mean.

And it is a very funny primer into what Midwesterners actually mean when they say what they say.

So highly recommend reading that.

I like that they give that to people just like here's what I might be telling you, which you may not read.

My wife is German, and I gave it to her.

I can see German being the opposite of that.

Okay, very different.

Another book. This is a good one.

Fate is the Hunters.

This is a really cool book.

It's a memoir of one of the early commercial airline pilots.

And it is wild to hear the stories about what flying was back in the day.

I'm a former management consultant.

I flew every week for almost six years.

And I never once had to worry about, am I going to make it to the other end of this flight alive?

That was not the case back then.

And so some of the stories about what it used to be like to be a pilot on some of these planes before modern aviation technology is fascinating and makes you really appreciate what we have.

Feels good to read a book like that being a software PM or engineer or whatever, like how different that life is.

Hardware is hard. It's not happy design.

Okay, next. Unless there's any other books you're going to share.

Okay, great. What's a favorite recent movie or TV show you've really enjoyed?

So I have two kids, I watch a lot of Bluey.

It's really good. I swear.

It brings me no shortage of joy.

But adult show not meant for four year olds that I have watched, I just finished the latest season of Emily in Paris.

Man, wonderful. I realize it's not the highest brow of television, but just like beautiful people in beautiful cities, solving problems that are not, you know, earth shattering.

Sometimes it is nice to just tune out.

Also, I'm learning French on Duolingo, slight plug for the app, I can understand a lot of the French that is being spoken.

And there is no better joy than having invested as much time as I have in French and actually being able to use it.

So huge fan of Emily.

That is so funny. What a fun Venn diagram of interests.

My mother -in -law loves Emily in Paris.

I saw someone tweeting about like, what would these are she on?

How is she still in Paris?

Yeah, you bet. Just not ask questions.

There's a lot. There's a lot of questions for the show that are better.

Do your favorite product you recently discovered that you really like other than Duolingo?

Last week I went to Home Depot and I bought a new ladder and ladder innovations.

You don't think, you know, of often, but you can make one of the legs go a little bit further than the other leg.

And as somebody like myself who has a house that is built on a slight slope, every time I go up in my ladder, I take my life in my hands.

But with this ladder, I'm always even I cleaned my gutters twice last week, just because of how awesome this ladder has, how much this ladder has changed my life.

So ladder innovation, I don't think it gets talked enough about.

And so I'm happy to give it the spotlight it deserves.

I appreciate you doing that.

This the first ladder recommendation we've had on the podcast.

Two more questions.

Do you have a favorite life motto that you really find useful and worker in life they share with folks?

This probably will not be much of a surprise based on how I've talked about our willingness to test things, but you miss 100 % of the shots that you don't take.

I'm a big fan of just trying things even if your possibility of success is not 100 because you learn a lot along the way.

So Final question. Do you have any fun traditions at Duolingo amongst either the PM team or the company in general that might be delightful to share?

We have way too many traditions to count.

I will share the weird tradition that we do at every retention standup.

And this started during the pandemic.

We obviously used to stand up in person.

And then when we went remote, we did this thing where whoever's the last person to go would count down three, two, one.

And then we'd all try to clap at the same time, which was fun and dorky, but we fell in love with it.

And afterwards, I can't tell you why, but trying to synchronize a clap via Zoom and then all shouting yeehaw.

I did this in a phone booth the other day.

And after I came out, someone told me, you know that those aren't as soundproof as you think, but you know, when you get a good opportunity to give a yeehaw, you kind of can't pass up on it.

So I love these little things like they're so, you know, they sound so minor, but they're such important elements of team culture and tradition and so important for PMs to find ways to just have fun and do something ridiculous.

I will say it took a while to get people behind shouting yeehaw.

But now that we have people doing it, you can't take it away from there.

We all love it. Oh man, I called our all hands for a while, y 'all hands.

Feel free to steal that.

You get it, Lenny. Yeah, I get it.

Jackson, this is incredible.

I feel like people are going to listen to this with notebooks and just like, okay, here's a bunch of ideas we should try with whatever we're working on, whether it's streaks or not.

Thank you so much for being here.

Two final questions.

Where can folks find you online if they want to reach out, learn more, learn more about Duolingo.

I know you're hiring product managers, so share more there.

And finally, how can listeners be useful to you?

Yes, you can find me on LinkedIn.

That is where most of my online social media is.

So Jackson, Shuttleworth.

And then how people can be useful to me.

Yes. As you said, we are hiring, we're actually hiring for my team.

Are you interested in thinking about streaks as much as we do?

We might be the right home for you.

So please, you can apply on our website.

But we're also hiring for a number of other product management roles, and they're all as thrilling as this work is.

And then I'm always interested about how other companies have implemented streaks and what they've learned.

And so what I'd say is if you're a company who's implemented a streak, maybe in a different way than Duolingo has, or you found a whole ton of success.

And another vector, another element to the feature that we didn't talk about today, I would love to know more.

I used to catalog basically every streak I found out there.

And as it's become more of a popular feature, it's just been hard to keep up on.

So if you have interesting streak insights to send my way, I would love to hear them.

I love that. A collection of all the best ways of doing streaks.

Jackson, I just want to say congrats to your team and you for having so much impact.

This is like the dream of a lot of PMs and teams is to see this much impact and continue to ship winds.

And so congrats. Nice work.

Thank you very much.

And with that Jackson, thanks so much for being here.

Yeah, thank you, Lenny.

This was a lot of fun.

Same. Bye, everyone.

Thank you so much for listening.

If you found this valuable, you can subscribe to the show on Apple Podcasts, Spotify, or your favorite podcast app.

Also, please consider giving us a rating or leaving a review, as that really helps other listeners find the podcast.

You can find all past episodes or learn more about the show at Lenny's podcast .com.

See you in the next episode.

[Duolingo의 140억 달러 성장을 이끈 핵심 엔진: '스트릭(Streak)'의 모든 것]-[Behind the product: Duolingo streaks | Jackson Shuttleworth (Group PM, Retention Team)]

📋 Summary

Duolingo의 성장 엔진: 스트릭(Streak)의 심층 분석

1. 스트릭의 본질: 습관 형성과 손실 회피

2. 진화하는 스트릭: XP에서 1레슨으로

3. 600번 이상의 실험: 테스트의 힘

4. 유연성과 완벽함 사이의 균형

5. 성공적인 기능 설계를 위한 조언

🎯Key Sentences

📝Key Phrases

📖 Transcript