Which one should you use?
If you have never formally tested yourself, start with the JLPT level test. It is the fastest way to stop guessing which textbook, which vocabulary list and which grammar set you should actually be working on — and knowing your level is what makes every other decision cheap.
If you are in the first weeks, the kana quiz is the one that matters. Reading hiragana and katakana without hesitation is the single prerequisite for everything else in Japanese, and the quiz tells you precisely which characters are still slow.
If you are travelling to Japan or already living there, take the everyday kanji sign test. It measures something the JLPT never examines: whether you can read the fixed labels that run daily life. Plenty of people pass N3 and still cannot start a washing machine.
Why interactive beats reading
Testing is not just measurement — retrieving an answer from memory strengthens that memory far more than re-reading the same information does. That is the whole mechanism behind spaced repetition, and it is why every one of these tools makes you answer before it explains. A wrong answer you had to commit to teaches more than a right answer you were shown.
The natural next step after any of them is to turn the gaps into a review schedule. That is what the Kanjijo app does: exclusive mnemonics for every kanji and vocabulary word, an SRS engine that times each review for the moment before you forget, an OCR scanner for reading the real world, home and lock screen widgets, and a full N5–N1 path with grammar, JLPT reading and listening practice, mock tests, conversation, shadowing and dictation.
Then keep the momentum
Kanjijo is the app these tools point at: OCR scanner, home, lock screen and interactive test widgets, exclusive kanji and vocabulary mnemonics, an SRS engine, the full N5–N1 kanji, vocabulary and grammar banks, JLPT reading and listening practice, mock tests, conversation, shadowing and dictation. Free on iPhone.
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