Vocabulary is the bottleneck in Japanese. Not grammar — grammar for any exam level fits in one book. Vocabulary takes months at JFT-Basic level and years at the higher JLPT levels.
Spaced repetition is how people actually hold thousands of words. Everything else works for a few hundred and then collapses.
What it is
You review each item just before you would have forgotten it. Items you find easy come back in a week, then a month, then a year. Items you keep failing come back tomorrow.
The effect is that your daily review load stays roughly constant while your total vocabulary grows indefinitely. Reviewing a list of 2,000 words by hand takes hours; reviewing 2,000 words with spacing takes about twenty minutes, because most of them are not due.
This is one of the better-established findings in the psychology of memory, and it is the reason a free app outperforms a notebook.
How to actually use it
Daily, without exception. This is the whole thing. Spacing algorithms assume you show up; skipping three days produces a backlog that feels punishing and is the most common reason people quit.
Twenty minutes daily beats two hours on Sunday, decisively.
Twenty new items a day. Thirty at higher levels. Not a hundred — the new items are not the work, the reviews are, and a hundred new cards today is a wall of reviews in four days.
Clear the reviews before adding new ones. If reviews are taking too long, add fewer new cards. Never skip reviews to add new material; that is how the backlog starts.
Whole sentences, not word pairs. A card reading “でんしゃ = train” produces recognition without usability. A card with a sentence carries the particles, the register and the way the word is actually used.
Pair confusables on the same card. 電車 and 電話. 病院 and 美容院. The exams build wrong answers from near-misses, so learn near-misses together.
Delete cards you hate. A card you consistently fail and resent is usually badly made. Rewrite it or remove it. Ten cards you review beat fifty you avoid.
What to put in
For JFT-Basic, weight it hard towards the exam’s world — numbers, times, dates, shops, transport, the workplace, the hospital, housing. Relevance beats volume on this exam. See how many words you need.
For JLPT, follow your level, and accept that from N3 upwards this is a daily commitment measured in months. See vocabulary by JLPT level.
What it does not do
It does not make words automatic. Spaced repetition builds the inventory — you know the word when asked. Moving from “I know this” to “I did not notice I knew this” takes reading and listening, in volume.
You need both. Learners who only do flashcards develop a large passive vocabulary they cannot use at speed, which is exactly the problem in a timed listening section.
It does not fix grammar. Different skill, different practice.
The tools
Anki is free on desktop and Android, is the most configurable, and has a genuinely ugly interface. Several friendlier apps do the same job.
The algorithm matters more than the app. Check that whatever you use actually schedules by forgetting curve rather than by streak or by however you feel today. Gamification is motivating; it is not a review schedule.
The honest part
This works and it is dull. The daily twenty minutes in month three, when nothing feels like it is improving, is the entire method.
That is also where most people stop — see staying consistent for what actually helps.