How Duolingo designs product (and why)

A playbook for designing for 500 Million users with high retention.

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I’m back and thank you for your patience as I recover from our annual, BeMore Festival 2023 and this week, ADPList crossed over 100 Million Minutes of Mentorship Session, which I’m told, makes this community the largest mentorship platform on the internet. Friggin’ mind-blowing.

This week, we’re going to 🔒 share exclusive insight 🔒 on, Duolingo.

This is the most mind-blowing education app.

Duolingo is one of the world’s most successful learning-based businesses. In 2022, it made nearly half a billion dollars in revenue (a 46% increase from the year prior) and had 16.3M daily active users.

But it’s not all good, here’s Duolingo’s big challenge…

It’s easy to be excited about starting a learning journey. But it’s much harder to stick with learning than most people think. A recent study by the MIT found that online courses only have a 4% retention rate. But Duolingo has been remarkably successful keeping people engaged with digital learning. They boast a daily active user retention rate of about 55%.

Why? Because they use psychology and behavioral science to keep us learning.

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How Duolingo designs product

Habits are actions performed without conscious thought — like grabbing your morning cup of coffee or going to the gym every day after work.

That’s why turning an app into a habit is the holy grail for every product — and Duolingo has managed to do for millions of users. To understand how…

Enter “Habit Loop,” describes the basic structure behind every habit.

Habit Loops consist of three parts, and all three parts must be present to create a habit.

1. The trigger (or cue)

2. The routine

3. The reward (or feedback)

Playbook 1: Design to create “triggers”

Triggers, also called cues, signal that it’s time to perform a habit. For me, waking up every morning triggers a craving for a cup of coffee — not because I want one but because it’s something I do every morning. 

Duolingo uses several triggers to get you to open the app: 

1. Emotional Manipulation

Duolingo is famous for its owl character named Duo. He’s got quite a personality (as well as a sometimes NSFW crush on singer Dua Lipa).

He’s an adorable mascot that the brand uses to manipulate its users' emotions and actions. For example — if you don’t use the app for a while you’ll start to get emails with subject lines like: 

• “You made Duo sad 😢”

• “Keep Duo happy”

2. Push notifications

One of the most common ways apps can trigger habits is by using push notifications. Especially those that pull psychological levers like Scarcity, Loss Aversion, or Commitment & Consistency.

3. Email Reminders

Duolingo knows that if users won’t respond to a push notification that the inbox is the next logical place to send a trigger. Their emails are simple, effective, and include: 

• Actionable subject lines with concrete language: “Hi Jen, take 5 minutes to practice Chinese today!”

• Simple layout with a clear call to action: “Start a lesson”

• Personalized streak information to push users to act before they break their streak: “Current streak: 1”

Playbook 2: Design to create “routine”

The routine is the habit itself. My morning coffee routine includes washing out my favorite mug (even if it’s clean), making espresso, frothing milk, and stirring in half a teaspoon of sugar. 

Duolingo’s customer experience is full of psychological strategies that get people hooked on the “routine” of learning a language, including: 

• Pre-commitment

• Social motivation 

• Goal Gradient Effect & Chunking

• Fixed Rewards: XP and Questions

• Variable Rewards: XP Boosts 

• Streaks

1. Pre-commitment

Pre-commitment, a proven motivational strategy, encourages people to commit to future actions.

Duolingo, prompts users to make specific pre-commitments to their learning goals. During onboarding, users set a daily time goal (left), and later, commit to maintaining a daily streak (right), by using the app daily.

If you want to include pre-commitment in your engagement strategy, follow Duolingo’s example by creating specific and actionable goals. For example:

❌ Don’t say: “Do you want to exercise at all/more/much more?”

✅ Do say: “Do you want to exercise on your Peloton bike 3, 5, or 7 days a week?”

Credit: Ella Keen Allee

2. Social Nudge/Motivation

Social motivation, or competition, boosts workout performance, healthy habits, and reaction times. Duolingo employs leaderboards to maintain user engagement, offering various leagues and a Diamond Tournament. However, competition might not suit all experiences, like apps tracking sobriety or quitting smoking, where public failure can be detrimental.

Assess if competition aligns with your users, goals, and brand.

3. The Famous Streaks

Duolingo's streaks keep you motivated to practice your chosen language daily, but breaking them can be demoralizing.

To address this, Duolingo allows users to "freeze" their streak.

This means you can miss a day without losing your progress, as long as you've consistently learned for a certain number of days beforehand. It strikes a balance between motivation and life's interruptions for a more positive language learning experience.

Credit: Duolingo Blog

Playbook 3: Design to create “rewards”

Rewards are the payoff you get from performing your habit. For example, my morning coffee habit gives me a quick boost of caffeine, fat, and sugar that my body craves (for better or for worse).

Duolingo includes a variety of rewards in its experience that make every correct question feel amazing — kicking up a little dopamine, the feel-good hormone in your brain). Here are a few of the ways they reward users: 

• Celebrations

• XP & Quests

• XP Boosts & Chests

• Achievements & Badges

1. Celebrations

Completing a lesson isn't just about gaining language proficiency; it's also an opportunity for a bit of celebration. Duo the Owl, along with another delightful character, breaks into a spontaneous dance routine. While this may seem like a minor gesture, it wields significant power in terms of user engagement and retention. This strategy leverages the psychological phenomenon known as Confirmation Bias, which asserts that people are naturally inclined to favor information that aligns with their pre-existing beliefs and actions. So, when users successfully finish a lesson and witness these endearing characters dancing, it ignites a sense of accomplishment. Simultaneously, it reinforces their conviction that their choice to learn a language with Duolingo is a wise one, creating a positive feedback loop that keeps them coming back for more language learning adventures.

2. Achievements and Badges

In mobile apps like Duolingo, digital badges are a popular gamification feature, keeping users engaged by motivating them to earn and showcase achievements. But do badges actually work? Here are the major statistics:

• 87% of users who earned a digital badge were more engaged as a result of their digital reward.

• 76% of business units said digital badges motivate employees.

Actionable insights on how Duolingo designs

To close, here’s a quick recap of my biggest takeaways:

1. Designing Habit Loops is a big win for high retention.

2. To achieve activation, design for creating Triggers:

   1. Emotional Manipulation

   2. Push Notifications

   3. Email Reminders

3. To achieve retention, design for establishing Routines:

   1. Pre-commitment

   2. Social Motivation

   3. Streaks

4. To achieve delight, design for delivering Rewards:

   1. Celebration

   2. Achievements Moments

5. Leveraging the Habit Loop (Trigger, Routine, Reward) model to design for both great user engagement and retention.

That’s it for this week! What else do you think would be helpful? Hit me up if you have any stories, feedback, or insights to share. Have a productive & fun week! 🙏

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