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Do you have what it takes to be a legend? Discover how we developed Legendary Levels, our final new level experience in Duolingo. We'll also share a behind-the-scenes look at how we've used A/B testing to improve the feature over time!

Duolingo’s mission is to develop the best education in the world and make it universally available. We always strive to balance this goal with the need to build a sustainable business by developing exciting new features for our subscription service, Duolingo Plus, to delight our subscribers as they learn a language.

In a previous post, we talked about how we recently created a Plus feature to help subscribers better learn from their mistakes. In this blog post, we’ll highlight how we developed our latest Plus feature, Legendary Levels. With this new feature, we introduced an updated final level experience. Now you can finally showcase your language mastery and prove you’re a language-learning legend!

Making the Plus experience legendary

Over the last few months, we set out to develop a new feature for Duolingo Plus to get our learners even more excited about learning with Plus.

Through multiple rounds of in-depth user interviews, we heard learners -- especially those learning with Duolingo for a while -- were looking for new ways to challenge themselves and prove they had mastered different content areas.

In Duolingo, we introduce learners to sets of words through skills, colorful themed circles that make up the home screen. Each skill has five levels, and each level teaches you new vocabulary and grammar in increasingly challenging ways. Once a learner reaches the last level, their skill turns gold, signaling completion of the skill.

We wondered how we could create new ways for skills to challenge our learners in response to their feedback. What if we added an even harder level above gold?

We approached this problem Duolingo-style, focusing on how we could make this new level feel challenging, rewarding, and fun. After having seen gamification prove successful in the past, our team took inspiration from game boss battles to design a new sixth and final skill level: Legendary!

Adding a sixth and final skill level

We wanted the Legendary experience to look and feel different from other levels of Duolingo. This led us to explore a new visual design for skills mastered at the Legendary Level. We hoped this new look would be something learners would be excited to earn as a way of highlighting their course progress!

Two illustrations of a skill at the legendary level. Exploring different visual treatments for Legendary skills. One has darker purple and a gold crown, the other has lighter shades of purple.

Exploring different visual treatments for Legendary skills.

In order to reach Legendary Level, learners must progress through a series of hint-free, difficult lessons. We created these using machine learning for an individualized but rigorous experience. In the lessons, learners spend substantial time reading, writing, listening, and speaking in the language they are learning, making this boss battle a true test of one’s language skills.

Screenshots of the initial design for Legendary Levels. On the left, the purple legendary level option is available when you click on a golden skill, under the skill practice option. In the middle is the Duolingo owl chasing a purple crown that is just out of his reach, and below him is an explanation of the four timed challenges. On the right, after the Legendary Level is completed, the skill has turned purple.

Initial design for Legendary Levels.

Upholding our mission

Although we were developing Legendary Levels with Plus learners in mind, we wanted to align this feature with Duolingo’s mission.

To that end, we decided to make the Legendary Levels feature available to all learners. Learners using the free version of Duolingo can attempt to reach Legendary Level with gems, our in-app currency, rather than paying via subscription. Plus learners, however, have unlimited attempts at Legendary as part of their subscription, without paying gems. This way, we are able to keep access to this feature available for all our learners while providing an extra benefit to Plus subscribers.

Screenshot explaining that learners can access Legendary via gems for single attempts or Plus for unlimited attempts.

Users can access Legendary via gems for single attempts or Plus for unlimited attempts.

Testing everything

At Duolingo, we try to A/B test as much as possible. This is a great way for us to understand the quantitative impact of changes to the product and learners' experience. Our initial A/B test of Legendary Levels on iOS was a resounding success, yet we knew we could make this feature even better.

Once we had some initial data on how learners were responding to the new feature, we set out on another round of user research. We wanted to know whether this gamified boss battle experience made learners feel like they had proven their mastery on Duolingo.

Through research, a few areas for improvement emerged. The Legendary lessons were timed to create an extra challenge and help differentiate the experience from traditional lessons. But, learners reported feeling this was overly punishing. Doing something quickly doesn’t necessarily signal mastery. Instead, accuracy was more important to our learners. We swiftly iterated on the feature and switched from timed lessons to lessons that only allowed learners to make up to three mistakes.

Screenshots of the Duolingo owl explaining the legendary level, before and after the change. Switching from timed sessions (left) to limiting the number of allowed mistakes (right).

Switching from timed sessions (left) to limiting the number of allowed mistakes (right).

Looking at data from our A/B test, we also realized our machine learning algorithm designed to make Legendary challenging was a bit too hard. We ran a follow-up A/B test to make the sessions slightly easier and awarded more XP for completing these hard Legendary lessons. This increased the number of Legendary lessons by 4%. We even redesigned the look and feel of Legendary to help make it feel extra special!

Updating the look and feel of Legendary to make it extra-special! A purple Duolingo owl looks up at the floating, sparkling purple legendary crown, and the owl's pupils are enormous and he looks hyponotized.

Updating the look and feel of Legendary to make it extra-special!


Legendary Levels have now been launched on iOS and Android. Learners have loved showing off the exclusive new look of their skills. We’re working on bringing Legendary to web next!

Every day, our subscribers are getting the chance to challenge themselves and prove they have what it takes to become a legend. We’re excited to keep investing in this feature and continue improving our subscribers' learning experience. Stay tuned for more updates!