the scheduler
The FSRS spaced repetition app built for iPhone
Most flashcard apps still default to SM-2, an algorithm from the 1980s. Imprimo runs FSRS, the Free Spaced Repetition Scheduler, from the very first card, so each review lands just before you would forget. The result is fewer cards a day for the same retention, natively on iPhone and iPad, fully offline.
why it matters
FSRS vs SM-2 at a glance
| FSRS (Imprimo) | SM-2 (legacy) | |
|---|---|---|
| Recall prediction error (open benchmark, mid-2025) | ~4% | 13-15% |
| Daily reviews at same retention (FSRS simulations) | 20-30% fewer | Baseline |
| Default in Imprimo | Yes, from day one | No SM-2 mode |
| Personalized weights | On-device optimizer | Fixed ease formula |
Sources: the open FSRS benchmark, July 2025, the last version that still listed SM-2, and the FSRS project's ABC of FSRS for the simulation figure.
FSRS from the first card
No legacy SM-2 mode and nothing to configure. Imprimo runs the modern scheduler out of the box, so your very first review is already optimized.
Fewer reviews, same retention
FSRS times each card for the moment just before you would forget it. The FSRS project's simulations put the saving at 20 to 30% fewer reviews for the same recall.
Personalized on-device optimization
Once you have enough review history, an on-device optimizer tunes the scheduling to your actual memory, with no data leaving your phone.
Calm by design
Native iPhone review with swipe-to-rate and haptics, offline support, and streaks treated as a passive stat rather than a pressure mechanic. The schedule does the work so you don't dread the queue.
faq
Common questions about FSRS on iPhone
What is an FSRS flashcard app?
An FSRS flashcard app schedules reviews with the Free Spaced Repetition Scheduler, a modern algorithm that predicts when you are about to forget each card and shows it just before that point. Imprimo runs FSRS on iPhone from the first card, with no older SM-2 mode to enable.
Is FSRS better than SM-2?
For most learners, yes. In the open FSRS benchmark's mid-2025 results, FSRS predicted recall with about 4% error against 13 to 15% for SM-2, and the FSRS project's simulations suggest 20 to 30% fewer daily reviews at the same retention target.
Is there an FSRS app for iPhone?
Yes. Imprimo is a native iPhone and iPad app that uses FSRS by default. Anki also supports FSRS as an opt-in setting, but its official iOS app costs a one-time fee and ships with SM-2 as the default.
Does FSRS work offline?
In Imprimo, yes. Scheduling and review run on-device, so you can study without a connection. An on-device optimizer also personalizes your scheduling once you have enough review history.
related reading
Go deeper on scheduling and study systems
ready when you are
Study with the modern scheduler, not a 1980s one
Imprimo runs FSRS from the first card, times every review, and works offline on your iPhone.
Download on the App Store