Reviews are the meat and potatoes of The Korean Vocabulary App. Up until now they've all run on the same 9-stage ladder where if you answer a word correctly and it climbs a rung, miss it and it slides back down. The intervals on the rungs ranged from 4 hours to 4 months. Simple and effective, but also a lot of work because...

The ladder has a blind spot: it treats every word, and every learner, exactly the same. The word you've nailed eight times in a row and the word that keeps slipping through your fingers both march up and down the same nine rungs on the same schedule. Your memory doesn't work like that, and your review queue shouldn't either.

Meet FSRS

That's why we're switching to FSRS (Free Spaced Repetition Scheduler) — an open-source algorithm that builds a little model of your memory for each word: how stable it is, how often it's tripped you up, how long since you last saw it. Then it schedules the next review for right before you'd forget.

Hold on, an algorithm has a model of my brain? A tiny one, yes — and it's in good company. FSRS comes from the same family of algorithms that Anki now uses by default, and the research behind it is genuinely impressive.

For the past month FSRS has been running silently alongside the standard SRS ladder, scheduling every one of your reviews in the background without changing anything you see. That let us fit the algorithm to how people actually learn Korean in this app, and we'll keep re-tuning it every month as more review data comes in. Once you have enough review history, it even gets fitted to your memory specifically.

The Part You'll Actually Notice

FSRS asks for roughly 70% fewer reviews per day than the fixed SRS ladder, while maintaining the same retention. In our side-by-side data, the ladder wanted about 23 reviews per person per day and FSRS wanted about 7. So if your review queue suddenly looks suspiciously short, don't panic — that's how it's supposed to work. (Yes, a language app is bragging about making you study less. Wild, I know.)

And don't worry, none of the other features you love are going away. Burn levels, XP, and streaks all carry over. Be advised that your burn level will now track how stable a word actually is in your memory, so it can move around a bit more than before — but nothing you've earned goes away, and burned words stay burned.

When Does This Happen?

• Today — smart scheduling is opt-in. Flip it on in your profile, or from the popup on your dashboard.
• Between now and the switch — you can switch back anytime, no harm done. Try it for a week and see how it feels.
• During the coming months — everyone moves over. We're conducting a phased rollout to make sure this works as well as we expect with real users and to hear their feedback. If they tell us to wait a little longer, we'll wait.

So how are you feeling about your shiny new robot scheduler? Hopefully good! If you have questions there's more detail on the FAQ page, and you can always reach us through the feedback button in the app or on Discord.

즐거운 공부 되세요!