Anki: The Complete Guide

Anki↗ is the free, open-source flashcard app that runs the science of spaced repetition for you. Used right — as a memory anchor for words you've already met in real input — it's the most powerful free tool in language learning. Used wrong, it's a soul-crushing word-list treadmill.

What it is

Anki is a free flashcard program built around spaced repetition (SRS). Instead of reviewing every card the same amount, Anki schedules each card to reappear just before you'd forget it — tomorrow, then in 3 days, then 8 days, then weeks, then months. Cards you find easy get pushed far into the future; cards you struggle with come back fast. The result: you spend your minutes only on the stuff that's actually slipping, not re-grinding words you already own.

Think of it as the progressive-overload log for your memory. A serious lifter doesn't lift the same weight every session and hope — they track reps and add load right at the edge of their capacity. Anki does exactly that for vocabulary: it finds the edge of your forgetting and parks a rep right there.

It runs everywhere. AnkiDroid (Android) and the desktop apps (Windows, Mac, Linux) are 100% free; AnkiWeb syncs them for free; only AnkiMobile on iPhone/iPad costs money (one-time, and it funds the whole project). The catch: Anki is famously ugly and unintuitive out of the box. That's the tax for it being free, open, and infinitely customizable.

Crucially, Anki is not a way to learn a language. It's a way to not forget what you're already meeting in real input — shows, books, conversations, podcasts. It's the spotter, not the workout. Mistaking the spotter for the workout is the #1 way people waste years in Anki and still can't understand a sentence.

The evidence

The whole thing rests on real, old, boringly-confirmed science:

• Hermann Ebbinghaus (1885) mapped the forgetting curve: memory decays exponentially after learning, but each review flattens the curve and slows future forgetting. Spacing reviews out beats cramming — his "spacing effect" has been replicated for over a century. See The Forgetting Curve & Memory.
• Retrieval practice (the "testing effect") — pulling an answer out of your head rather than re-reading it into it — produces dramatically stronger retention. Work by Roediger and Karpicke (2006) showed students who self-tested remembered far more long-term than students who restudied. Anki is a retrieval machine: every card forces a recall attempt before you flip it. See Retrieval Practice & Interleaving.
• Paul Nation, the leading vocabulary researcher, estimates you need to meet a word several times in meaningful context to truly acquire it, and that knowing the most frequent ~2,000–3,000 word families covers the vast majority of everyday speech. Anki is excellent at delivering those repeated encounters efficiently — but Nation is clear that deep word knowledge comes from context, not isolated lists. See Vocabulary Acquisition.

Now the honest part. Stephen Krashen would tell you flashcards aren't where language is acquired — language is acquired through Comprehensible Input (Krashen), messages you understand, ideally at the i+1 level. SRS is conscious learning, which Krashen treats as a "monitor," not the engine of fluency. The two camps reconcile cleanly: input builds the intuition; Anki just keeps the bricks from crumbling between input sessions. It accelerates how fast new words feel "yours," so your next book or episode is more comprehensible.

What the evidence does not support: memorizing pre-made 5,000-word lists of decontextualized translations and expecting to speak. That's grammar-translation logic in a shiny app — see Grammar-Translation (and Why It Fails). A word memorized as perro = dog and nothing else is a dead rep. A word you mined from a sentence you actually heard is a living one.

How to actually use it

No fluff. Here's the program that works.

1. Install the free stuff. Get Anki desktop (apps.ankiweb.net) and AnkiDroid if you're on Android. Make a free AnkiWeb account and sync. iPhone-only? AnkiDroid won't run, so either use desktop or buy AnkiMobile.

2. Don't download a giant pre-made deck. Repeat: do not start with someone's 10,000-card "Top Spanish Words" deck. You'll drown in 200 reviews/day of words you've never encountered, hate it, and quit in two weeks. The gym equivalent is loading 200kg on day one. You'll get hurt.

3. Make sentence cards from YOUR input. This is the move. As you watch, read, and listen, when a word or phrase keeps blocking comprehension, grab the whole sentence it lived in. Front: the target sentence (ideally with audio). Back: the meaning of the unknown word plus a quick gloss. This is Sentence Mining — context-rich cards crush isolated word = word cards because you're training recall in the shape you'll actually meet the language.

4. Follow the "1T" rule. Only mine sentences where there's one unknown thing (one new word or grammar point). If a sentence has three mysteries, it's not your i+1 yet — skip it, keep getting input, come back later.

5. Automate the boring part. Pair Anki with Language Reactor or Yomitan/Migaku↗-style tools that build a sentence card — text, translation, audio, even a screenshot — in two clicks straight from Netflix or YouTube. Card creation should take seconds, not minutes, or you won't keep it up.

6. Cap your additions. Add 5–15 new cards a day, no more. Reviews compound — 10 new cards/day becomes a sustainable ~30–80 reviews/day; 50 new cards/day becomes an unmanageable avalanche in a month. Consistency beats intensity. This is reps, not maxing out.

7. Do reviews daily, then close the app. Same time every day — bus, coffee, toilet, whatever. Be brutally honest hitting Again / Hard / Good / Easy; lying to the algorithm only lies to future-you. Then stop and go get real input. Anki is the warm-up, not the session.

8. Turn on FSRS. Modern Anki ships with the FSRS scheduler — a smarter algorithm than the old default. Enable it in deck options; it spaces cards more accurately so you do fewer reviews for the same retention. Free gains, literally.

9. Prune ruthlessly. A card you've gotten right ten times in a row but find boring? Suspend or delete it. A "leech" you keep failing? Either rewrite it with better context or cut it. Dead weight in your deck is dead weight in your routine.

The whole thing folds into your daily training — see Building Your Daily Routine. Five minutes of Anki to lock in yesterday's words, then an hour of input to meet tomorrow's.

Resources

• Anki — the desktop app and AnkiDroid are free. Search "Anki download apps.ankiweb.net". AnkiMobile (iOS) is paid and funds development.
• The official Anki Manual — genuinely the best documentation. Search "Anki manual". Read the sections on FSRS and deck options.
• Language Reactor↗ — browser extension to make sentence+audio cards from Netflix/YouTube. See Language Reactor & Immersion Tools.
• Yomitan (the maintained successor to Yomichan) — pop-up dictionary + one-click card export, excellent for Japanese and beyond.
• Migaku — a paid all-in-one immersion + Anki toolkit if you want card creation fully streamlined.
• AnkiWeb — free cloud sync across all your devices. Set it up first.
• Make Me Fluent / Refold↗'s Anki guides — practical, input-first setup walkthroughs. Search "Refold Anki sentence mining guide".
• "Fluent Forever" by Gabriel Wyner — popular book on building your own SRS cards (use it for technique; lean harder into context/input than the book's word-list bent).

Related

• Spaced Repetition (SRS)
• Sentence Mining
• The Forgetting Curve & Memory
• Retrieval Practice & Interleaving
• Vocabulary Acquisition
• Language Reactor & Immersion Tools
• Comprehensible Input (Krashen)
• Building Your Daily Routine