Japanese Grammar Checker
Paste a Japanese sentence and get it corrected — with the grammar rule behind every fix explained in English. Free, no account, no limit on how wrong you are.
What you get back
Here is a real example. Every correction names the grammar point, because knowing which character changed teaches you nothing about the next sentence.
You wrote
昨日友達に映画を見に行きました。
Corrected
昨日友達と映画を見に行きました。
Yesterday I went to see a movie with a friend.
1 correction — and why
友達に → 友達と
と marks the person you do something together with; に marks a target or destination. 行く already takes に for the place you are going, so the companion has to be marked with と — 友達に行く would read as "go to a friend".
More natural
昨日、友達と映画を観に行きました。
Why this exists
Lang-8 shut down. HiNative answers arrive hours later, if at all. italki costs money per correction. Meanwhile the question “is this sentence right?” is the single most common thing a Japanese learner needs answered, and it needs answering in seconds, not tomorrow.
This checker corrects particles, conjugation, word order, politeness register, and word choice, then explains each fix in plain English and estimates the JLPT level of what you wrote. Every check produces a permanent page you can link, bookmark, or send to whoever asked.
What it will not do
It checks Japanese sentences and nothing else — it is not a translator, a chatbot, or a homework machine. Input has to be in hiragana, katakana, or kanji, and one sentence at a time.
How this Japanese grammar checker works
- Paste one Japanese sentence into the box above, in hiragana, katakana or kanji.
- An AI model reads it and returns the corrected sentence, each change marked, and a plain-English explanation of the grammar rule behind it.
- You also get a more natural way to say it, an English translation, and an estimate of the JLPT level of what you wrote.
It is free and needs no account, and it covers every level from N5 to N1. Use it as a Japanese sentence checker for homework, for messages you are about to send, or to test a sentence you made up yourself.
Examples: how a Japanese sentence corrector fixes common mistakes
Three mistakes learners make all the time, and what the correction looks like.
A wrong particle after 行く
You wrote私は昨日学校を行きました。
Corrected私は昨日学校に行きました。
行く marks its destination with に (or へ), not を. を is for the thing you act on, or for the route you move through, as in 公園を歩く.
です stuck onto a verb
You wrote昨日は雨が降るでした。
Corrected昨日は雨が降りました。
でした attaches to nouns and adjectives, not to a verb in its dictionary form. A verb takes the polite ます ending, and the past is 降りました.
Past tense of an い-adjective
You wroteこの映画はとても面白かったでした。
Correctedこの映画はとても面白かったです。
An い-adjective carries its own past tense (面白い → 面白かった). To make it polite you add です after it; でした cannot follow a past-tense adjective.
Check Japanese grammar yourself first
A checker is fastest when you have already looked at the sentence once. Before you paste it, ask four questions:
- Why that particle and not the one next to it? If you cannot say, that is the word to check.
- Is the verb transitive or intransitive? 開ける and 開く are both correct Japanese, but only one says what you meant.
- Is it ている or た? ている covers both an action in progress and a resulting state.
- Is the politeness level the same from start to finish?
If a phrase is still in doubt, search it in a sentence corpus such as Massif. If real Japanese never uses it, it is very likely wrong whatever any tool says.
What a grammar checker can and cannot catch
A grammar corrector is good at particles, conjugation, word order and mixed politeness. It is weaker where a sentence is grammatical and still sounds odd: the は and が choice, a collocation Japanese people simply do not use, or a casual sentence sent to a teacher. For those, read the explanation attached to each fix and ask a native speaker when it matters. Want a walkthrough of these cases? See our guide to Japanese particle practice.
Japanese grammar checker FAQ
Is this Japanese grammar checker really free?
Yes. Checking a sentence costs nothing, and there is no trial and no card to enter. Usage limits apply.
Do I need an account to correct my Japanese?
No. Paste a sentence and the correction comes back without signing up. A free account is optional; it saves future checks made while you are logged in.
Which JLPT levels does the checker cover?
All of them, from N5 beginner sentences to N1-level writing. It also estimates the JLPT level of the sentence you wrote, so you can see whether your grammar is where you think it is.
How accurate is it compared with a native speaker?
It is reliable on the mechanical errors learners make most: particles, verb and adjective conjugation, word order and politeness mix-ups. It is weaker on nuance and on whether a phrase sounds natural to a Japanese reader, because that depends on context. For a CV, an email to a client or anything high stakes, have a native speaker read the final version.
Is what I paste kept private?
The sentence is sent to an AI model to be corrected, and each check is saved on a result page with its own unguessable link. Search engines are told not to index those pages, but anyone who has the link can open it, so do not paste anything personal such as names, addresses or passwords.
How is this different from Google Translate or DeepL?
A translator turns your sentence into English and quietly repairs the mistakes on the way, so you never learn what was wrong. This checker keeps your Japanese as Japanese: it shows the corrected sentence, marks each change and explains the grammar rule behind it in English.
Checking more than one sentence?
A free account saves future checks made while you are logged in. Use the correction in a new answer with Daily Japanese writing practice.
The checker stays free without an account. Usage limits apply. No card needed.