How Duolingo grows

Tested reducing the free trial from two weeks to seven days in several combinations with how many trials a user is eligible for. Beyond conversion, the shorter trial means experiment readouts come in 7 days instead of 14, so losing tests are killed sooner and more tests run per quarter.

After reading reviews where users asked to pay to remove ads, tested a one-time purchase of 30 ad-free days at $3, $5 and $10 instead of a subscription.

Purchase pages explain the mechanics: 'this is a seven day free trial; on day five we'll send you a notification to see if you still want your subscription.'

Iterated purchase button copy in A/B tests: 'Subscribe' (baseline) -> 'Start my free trial' (big uplift) -> 'Try for free' (better) -> 'Try for $0.00' (best; believed live). Part of ~400 concurrent A/B tests, many on the purchase flow.

Default: a notification is sent about 2 days before the free trial expires. Test: at trial signup, let the user choose which day they get that reminder. The extra step draws attention to the fact that a reminder is coming and they can cancel later, so users wait until day 5 or 6 to judge whether they are getting value instead of cancelling immediately.

Instead of dropping the standard Super Duolingo upsell into the onboarding flow, make the offer contextual to onboarding: ask 'How do you want to achieve your goals? With ads or without ads? Learn faster or at your own pace?' so the subscription is part of the onboarding answers. New users are far more likely to convert than existing ones.

Introduced ads in 2016 with a single placement: after a lesson is completed (not app open, not mid-lesson), still the only placement today. Team dogfooded the app daily to judge the feel, and A/B tested each ad change against retention, app closes and reviews.

Before deciding to launch ads in 2016, quantified complaints and negative reviews about ads per million DAU and compared them to complaints about other topics (e.g. a missing language course), alongside neutral retention in A/B tests.

A/B tested giving Explain My Answer (an LLM-based Max feature explaining your specific mistake) free vs keeping it in Max. Revenue impact was small, and LLM costs had fallen with better caching, so it moved to free. Practice Hub was also moved from Super to free. Rationale: free users are the word-of-mouth engine; big trade-offs are signed off by senior leaders including the CEO.

Duolingo changed its paywall call-to-action text to 'Try for $0.00' (released around January), replacing 'Try for free'.

'Free taste': a three-day, no-strings trial-like experience of Super or Max, with no auto-convert. User can convert during or after. Also used for paid-to-paid: Apple won't allow another free trial to an existing subscriber, but a Super subscriber can get a Max free taste and then return to Super. Aimed at users hesitant to start a real trial.

Duolingo's first monetization experiment (2016): users could buy a repair of a broken streak for about $1-3.

Ran a 1-2 year ads holdout, but no longer recommends year-long holdouts (they get forgotten and polluted by bugs). Now runs 3-6 month holdouts or long experiments on things like leaderboards (10 weeks to climb from lowest to top league) and push notifications, where novelty lifts fade.

Duolingo Plus (2017): no ads plus fully offline use; because the purchase page looked thin with two features, added a third line 'Support Duolingo's mission', echoing what users said in reviews.

Hearts (now Energy) limit new lessons after a number of mistakes; free users regenerate by practicing old content, watching ads, or (then) an IAP. Made unlimited Hearts a subscription feature. Also added a Practice Hub tab to the subscription (later made free).

Building on the Blinkist-style trial reminder paywall ('we'll remind you before the trial ends'), Duolingo tested letting users choose which day they get the reminder, drawing attention to the reminder promise.

Goal is clarity and confidence, not persuasion: explain in a timeline what happens on which day of the trial and when the user is charged; when switching plans, state clearly how much money they get back.

When a learner runs out of hearts/energy mid-lesson, position the choice as: if you don't continue you lose your progress; pay gems or start the free trial now to keep your progress and finish the lesson. Still shows a sense of progress so it isn't punitive.

Users are eligible for multiple free trials, spread over time, because they are in different life stages or didn't get to experience the benefits the first time. Each user faces the purchase decision three or four times. (Apple allows the intro offer once per SKU, so this needs workarounds.)

Instead of trialing the whole tier, offer a free taste of one feature in isolation: just one video call (part of the Max tier), then see if users convert.

Free tier shows ads: a mix of house ads promoting subscriptions and third-party ads. First ML use: optimize the mix of own-product promos vs external ads. Then predict which plan (Super vs Max) a likely subscriber will pick, replacing fixed per-tier ad ratios, using signals like past taps on a plan or engaging with a video-call lesson.

Many creatives promote Super as an ad at the end of a lesson; a bandit optimizes which creative works best for which user.

Duolingo's original model (~2013): the website was free; learners' translation exercises were crowdsourced into full article translations sold to outlets like CNN and BuzzFeed. Quality work pulled resources from teaching toward running a translation business.

US-only direct ad deals: one of Duolingo's eight characters (e.g. Lily) introduces the brand's ad with a short custom-written joke script, then the ad plays. Formats are Duolingo-built. Goal: cut programmatic volume substantially in 2026.

Added free trials to the subscription even though the core product was free and paid features (no ads, offline) did not need to be experienced. The trial removes payment hesitation.

Launched math as a separate app, planning one app per subject, then moved math, music and chess into the main app's course switcher with light promos. Picked subjects that are fun to teach on mobile, have existing demand, fit bite-sized skills and have a senior internal champion (skipped coding and running). Each took 6-12 months of prototyping and dogfooding.

Built a higher-tier subscription where users pressed a button to connect instantly with a human Spanish tutor, no booking. Users had requested it for years. Iterated to ease users in, then shut it down. Replaced by an AI video call with the character Lily.

Copy always states it's a three-day free period/preview and says 'Hey, you just earned this.' The reward chest used to sit on the learning path; moved it to after completing a lesson because earning it there felt more rewarding. Uses timers for urgency, and the subscriptions page says you can upgrade anytime and makes clear there won't be a surprise charge (so Super subscribers don't cancel).

At each lesson end an ML model picks between a programmatic ad and an internal ad (Super, Max, Duolingo English Test), maximizing LTV with purchase likelihood as the objective. If a user ignores the Super ad about three times it backs off. Internal ads are character-driven videos that explain the subscription features.

After a free taste ends, a home drawer comes up stating 'Your X benefits have ended' with two options: continue (free), or explore/resubscribe. Emphasis on being clear it has ended and that rejoining is easy.

Started with AdMob, then added Facebook, Flurry and later Unity to broaden demand. Blocked every category not brand- or young-audience-safe (gambling, sketchy games) and worked with networks on custom blocks (e.g. ads with three X buttons).

Basic plan gets non-AI features and a limited taste of AI; full/unlimited AI (e.g. Duolingo Max's voice role-play with Lily) requires a higher Pro/Max tier, to cover compute costs. Also seen at Perplexity, ChatGPT, Claude, ElevenLabs, Tolan.