Best Spaced Repetition Apps in 2026
But not every app that claims "spaced repetition" actually delivers. Some use crude interval systems. Others paywall the algorithm behind a subscription. In this guide, I'll break down every major spaced repetition app available in 2026 - what algorithm they actually use, what's free vs. paid, and which one fits your use case.
What Makes a Good Spaced Repetition App?
Before comparing apps, there are four things that separate a good SRS tool from a mediocre one.
1. The algorithm tier
The scheduling algorithm is the core of any SRS app. Not all are equal:
- Leitner boxes - Cards move between boxes based on right/wrong answers. Fixed intervals, no personalization. Used by Quizlet and many "spaced repetition" apps that aren't really doing spaced repetition.
- SM-2 - SuperMemo's 1987 algorithm. Per-card ease factors adjust intervals. Anki's default. Works, but has a known "ease hell" problem where difficult cards get stuck at short intervals.
- FSRS (Free Spaced Repetition Scheduler) - Published in 2022, peer-reviewed. Models your memory using three parameters (stability, difficulty, retrievability) and schedules reviews at the point where your recall probability drops to ~90%. Significantly more accurate than SM-2.
If an app can't tell you what algorithm it uses, it's probably not doing real spaced repetition.
2. What you get for free
Some apps give you the full algorithm on the free tier. Others paywall it. If the scheduling is behind a subscription, the free version is just a flashcard viewer - not a spaced repetition app.
3. Content quality
Pre-made decks save hundreds of hours, but community decks often have errors and missing context. Curated content with example sentences, translations, and grammar notes (conjugation patterns, gender rules, usage tips) makes a measurable difference in retention. Grammar notes in particular are a feature most apps completely lack - they give you the "why" behind a word, not just the "what."
4. Active recall modes
Passively flipping cards builds recognition but not production. Multiple study modes - typing, listening, matching - train different aspects of memory and produce stronger long-term retention.
The Apps Compared
1. Words on Repeat - Best Overall
Algorithm: FSRS | Price: Free (Pro: $5.99/mo) | Platform: Web (PWA), works on all devices
Words on Repeat uses the FSRS algorithm on the free tier - the same state-of-the-art algorithm Anki added as an opt-in feature in 2023, but here it's the default from day one. No configuration, no add-ons, no subscription required for the core study experience.
Strengths
- FSRS algorithm on the free tier - not paywalled, not opt-in
- 7 quiz modes including typing, listening, and speed review - all free
- 200+ curated decks across 12 languages with grammar notes on every card
- Import from both Anki (.apkg) and Quizlet (tab-separated text)
- AI word extraction from URLs and pasted text
- No ads, ever - dark mode, study streaks, and push reminders built in
- Works offline as an installable PWA - no app store needed
Limitations
- Free tier limited to 10 decks and 1,000 words (covers most learners through B2)
- Web-based PWA (installable to home screen, works offline - no app store listing)
What sets it apart from every other app on this list: every curated card includes an example sentence with translation and grammar notes - contextual tips like conjugation patterns, gender rules, and usage nuances. No other app includes this level of context on pre-made cards. For a full feature walkthrough with screenshots, see our detailed review.
Best for: Anyone who wants real spaced repetition without setup. Start studying in under a minute →
2. Anki - Most Customizable
Algorithm: FSRS or SM-2 (user choice) | Price: Free (desktop/Android), $24.99 (iOS) | Platform: Desktop, Android, iOS
Anki is the oldest SRS app still in active development. It added FSRS as an opt-in option in 2023, though it still defaults to the outdated SM-2 - and most users never discover the setting to change it. The real draw is complete customization - card templates with HTML/CSS/JS, thousands of community add-ons, and granular control over every scheduling parameter.
Strengths
- FSRS support (opt-in since 2023, but defaults to older SM-2)
- Complete customization of card templates (HTML/CSS/JS)
- Community deck library (quality varies widely, no curation)
- Free on desktop and Android
Limitations
- Steep learning curve - interface hasn't been updated in over a decade
- iOS app costs $24.99
- No built-in quiz modes beyond card flipping - everything else requires add-ons
- Community decks vary wildly in quality - no curation, no grammar notes
- Many users watch hours of YouTube tutorials before studying effectively
- No dark mode, study streaks, or progress dashboard without add-ons
Best for: Power users who want total control over card templates and don't mind extensive setup. Expect to spend hours configuring before you start studying effectively.
3. Quizlet - Familiar but Gutted
Algorithm: Proprietary (Leitner-like) | Price: Free (limited), Plus: $35.99/yr | Platform: Web, iOS, Android
Quizlet was the default study app for a generation of students. But since 2022, it has systematically moved features behind a paywall. The free tier in 2026 is a card flipper with full-screen video ads.
Strengths
- Classroom features (Quizlet Live, teacher dashboards)
- Diagram and image-heavy study sets
Limitations
- No real spaced repetition algorithm - not SM-2, not FSRS, even on the paid plan
- Learn mode, test mode, and offline access all paywalled ($36/yr)
- Free tier shows full-screen video ads between study sessions
- Community decks have no quality control - errors and inconsistencies are common
- No grammar notes, example sentences, or contextual hints on cards
Best for: Teachers who need classroom tools. Students who need image-heavy study sets for subjects like anatomy. For everyone else, the free alternatives are better.
4. Memrise - Immersive but Expensive
Algorithm: Proprietary | Price: Free (limited), Pro: $79.99/yr | Platform: Web, iOS, Android
Memrise's selling point is native speaker video clips. But the spaced repetition is basic (proprietary, not FSRS or SM-2), the free tier is restrictive, and $80/year is steep - more than double what most competitors charge.
You can't create custom flashcards easily, and the fixed course structure means you can't study your own vocabulary - you learn what Memrise decides you should learn, in the order they decide. Best used as a supplement alongside a dedicated SRS tool, not as your primary study app.
Best for: Learners who want native speaker pronunciation videos and enjoy structured courses. Budget: $80/year.
5. Brainscape - Professional Content, Premium Price
Algorithm: Confidence-Based Repetition (CBR) | Price: Free (limited), Pro: $95.88/yr | Platform: Web, iOS, Android
Brainscape partners with publishers and educators to create professionally authored decks. The algorithm uses a 1-5 confidence scale - simpler than FSRS but more structured than Leitner. The main draw is expert-reviewed content for standardized tests (MCAT, bar exam, CPA).
At $96/year, it's the most expensive option on this list. The free tier is very limited. If you're preparing for a specific standardized test and want curated expert content, it's worth evaluating. For language learning or general study, the price-to-value ratio doesn't hold up against free alternatives.
Best for: Standardized test prep (MCAT, bar exam) with professionally authored content. Budget: $96/year.
6. MintDeck - Newer Mobile-First Option
Algorithm: FSRS | Price: Free (limited), Premium plans available | Platform: iOS, Android, Web
MintDeck is a newer app that also uses FSRS with a mobile-first approach and native apps.
However, it falls short in several areas: the curated deck library is much smaller than Words on Repeat's (fewer languages, fewer levels), cards don't include grammar notes or example sentences, there's no Quizlet import, and as a newer app it has a shorter track record. Words on Repeat offers a significantly more complete experience.
Best for: Users who want FSRS in a native mobile app and don't need extensive curated content.
7. Chunks - Phrase-Based English Learning
Algorithm: Adaptive spaced repetition | Price: Free | Platform: Web, iOS, Android
Chunks takes a different approach: instead of teaching individual words, it teaches language in multi-word "chunks" - collocations, fixed expressions, and common sentence patterns. The idea is based on the linguistic concept that native speakers retrieve pre-assembled phrases rather than constructing sentences word by word.
Strengths
- Phrase-based approach teaches natural collocations rather than isolated words
- AI translation practice - translate sentences and get instant feedback
- Spaced repetition adapts review intervals based on performance
- Free to use
Limitations
- English only - no other target languages
- Pre-built content only - no custom decks or user-created cards
- Algorithm not specified (not FSRS or SM-2)
- No import from Anki or Quizlet
- No quiz modes beyond card review and translation practice
Best for: Learners focused specifically on English who want to build natural-sounding phrases rather than study individual vocabulary. Limited to English only.
Feature Comparison Table
| Feature | Words on Repeat | Anki | Quizlet | Memrise | Brainscape | MintDeck | Chunks |
|---|---|---|---|---|---|---|---|
| Algorithm | FSRS | FSRS/SM-2 | Basic | Proprietary | CBR | FSRS | Adaptive |
| Free spaced repetition | Yes | Yes | No | Limited | Limited | Limited | Yes |
| Quiz modes (free) | 7 | 1 | 1 | 3 | 1 | 2 | 2 |
| Curated decks | 200+ | Community | Community | Courses | Professional | Some | Pre-built |
| Grammar notes | Every card | No | No | No | No | No | No |
| AI word extraction | Yes | No | No | No | No | Yes | No |
| Anki import | Yes | N/A | No | No | No | Yes | No |
| Quizlet import | Yes | No | N/A | No | No | No | No |
| Offline support | Yes (PWA) | Yes | Paid only | Paid only | Paid only | Yes | No |
| Ads on free tier | None | None | Full-screen video | Yes | No | No | None |
| Dark mode (free) | Yes | Via add-on | Paid only | Yes | No | Yes | Yes |
| Languages | 12+ | Any | Any | 16 | Any | Several | English only |
| Annual price | Free/$59 | Free/$25 iOS | $36/yr | $80/yr | $96/yr | Varies | Free |
Which App Should You Choose?
Choose Words on Repeat if:
- You want real spaced repetition (FSRS) without any setup or configuration
- You want 7 quiz modes without paying - typing, listening, matching, and more
- You want curated decks with grammar notes and example sentences on every card
- You're coming from Quizlet and want the same ease of use without the paywall or ads
- You want to import existing cards from Quizlet or Anki and keep studying
- You want to start studying in under a minute, not hours of configuration
Choose Anki if:
- You want total customization of card templates (HTML/CSS/JS)
- You're comfortable with a steep learning curve and troubleshooting add-ons
Choose Quizlet if:
- You need classroom features or teacher tools
- You study image-heavy subjects (anatomy, geography)
Choose Memrise if:
- You want native speaker video content and structured courses
- You're willing to pay $80/year
Choose Brainscape if:
- You want professionally authored content for standardized tests
- Budget isn't a primary concern ($96/year)
Choose Chunks if:
- You're learning English specifically and want to study natural phrases and collocations
- You prefer pre-built content over creating your own cards
For a deeper comparison of Anki, Quizlet, and Words on Repeat specifically, see our head-to-head comparison.
The Science Behind Spaced Repetition
Hermann Ebbinghaus discovered the "forgetting curve" in 1885 - without review, you forget approximately 70% of new information within 24 hours. Spaced repetition fights this by scheduling reviews at the optimal moment: long enough to challenge your memory, short enough that you can still recall.
Modern research confirms that algorithmically optimized spacing outperforms fixed schedules by 20-40% (Settles & Meeder, 2016; Tabibian et al., 2019). FSRS takes this further by modeling each learner's memory individually rather than using population averages.
The practical result: a well-optimized FSRS schedule achieves 90%+ retention with roughly half the daily review load of a fixed-interval system. You spend less time reviewing and remember more - that's the whole point.
For a detailed explanation of how FSRS works in practice, see our guide to spaced repetition.
Frequently Asked Questions
What's the best free spaced repetition app in 2026?
Words on Repeat offers the most complete free tier: FSRS algorithm, 7 quiz modes, 200+ curated decks with grammar notes, offline support, and no ads. Anki is also free on desktop and Android but requires significant setup and has no built-in quiz modes or curated content.
Do I need spaced repetition or is regular flashcard review enough?
Regular review (flipping through your whole deck) wastes time on cards you already know and under-reviews cards you're about to forget. Spaced repetition solves both problems by scheduling each card individually. Research shows 20-40% better retention with the same or less study time. If you're studying more than a few dozen cards, SRS is worth it.
FSRS vs SM-2 - does the algorithm really matter?
Yes. SM-2 uses a single "ease factor" per card that can spiral downward ("ease hell"), causing difficult cards to appear too frequently while easy cards appear too rarely. FSRS models your memory with three independent parameters and adapts more accurately. In practice, FSRS achieves the same retention with fewer daily reviews.
Why do so many apps claim "spaced repetition" when they don't use it?
Because "spaced repetition" is a marketing buzzword. Showing missed cards more often (Leitner boxes) is technically "spaced" but doesn't model your memory or optimize review timing. Real SRS uses a mathematical model (SM-2 or FSRS) to predict when you'll forget each card. If an app doesn't name its algorithm, it's almost certainly using basic Leitner or random intervals with branding.
Can I switch between apps without losing progress?
Words on Repeat imports from both Anki (.apkg files) and Quizlet (tab-separated text export). Your cards get FSRS scheduling immediately after import. See our step-by-step migration guide for details.
References
- Ebbinghaus, H. (1885). Memory: A Contribution to Experimental Psychology. Translated by H.A. Ruger & C.E. Bussenius, 1913. psychclassics.yorku.ca
- Settles, B. & Meeder, B. (2016). "A Trainable Spaced Repetition Model for Language Learning." Proceedings of the 54th Annual Meeting of the Association for Computational Linguistics (ACL). aclanthology.org/P16-1174
- Tabibian, B., Upadhyay, U., De, A., Zarezade, A., Scholkopf, B. & Gomez-Rodriguez, M. (2019). "Enhancing Human Learning via Spaced Repetition Optimization." Proceedings of the National Academy of Sciences, 116(10), 3988-3993. doi:10.1073/pnas.1815156116
- Ye, J. (2022). "A Stochastic Shortest Path Algorithm for Optimizing Spaced Repetition Scheduling." ACM SIGKDD Workshop. doi:10.1145/3534678.3539081
- Open Spaced Repetition. FSRS4Anki - Free Spaced Repetition Scheduler. github.com/open-spaced-repetition/fsrs4anki