Hearts are used as a way of pacing Duolingo lessons to discourage binging behavior, which is shown to be ineffective for learning a new language (consider users who don’t care how many mistakes they make but simply progress through lessons to achieve status). You can lose Hearts by answering incorrectly too many times, which has been encouraging users to pay closer attention to what they are answering before hitting “check”. You will start out with 5 Hearts each day!
Why do we have Hearts?
Because it’s better for learning! Our research shows that if people advance too quickly on Duolingo in one day, it can actually negatively impact their learning because they are less likely to remember what they’ve learned. We know that users learn best when they study every day and take the time to practice and review what they’ve learned. The Hearts feature encourages users who are making mistakes to take a breather and review previous lessons before moving forward.
How can I earn a Heart?
You practice previous material to restore it a lost Heart. Tap on the Hearts tab and tap "Practice". Each lesson practiced will restore one Heart. Typically, your next Heart will refill every 5 hours, so your total of five Hearts will restore within 24 hours.
For those who still want to binge on Duolingo without taking a break or taking the time to review lessons, Hearts can also be refilled with Gems.
How can I have unlimited Hearts?
All Duolingo Plus subscribers have unlimited hearts as a benefit of their subscription. You can learn more about enabling this feature here.
What about other platforms?
Hearts are currently available to Android and iOS users. We do not currently have plans to bring this to Web.