Free Japanese grammar checker for particles, verb forms, and keigo
Correction
Why it changed
In Wonderglot stories, every reply you send gets this same check, plus one-tap word definitions and voice chat. Practice in a Japanese story
Updated 2026-10-26 · Published by Wonderglot (DigitalCarbon Inc). The interactive Japanese grammar checker above uses the same correction judge that powers reply feedback in Wonderglot Japanese stories.
Key takeaway
In Japanese, a single particle swap (は vs. が, に vs. で, を vs. が) or an intransitive verb paired with を changes who did the action. The free Japanese grammar checker above highlights the exact character span that changed and explains the particle or conjugation rule in plain English—and when you want daily Japanese reading practice and Japanese conversation practice, Wonderglot runs this same check on your replies inside ongoing stories (free messages every day + permanently free word lookups; Plus at US$8.99/month or US$59.99/year).
Why translating Japanese back into English fails to catch particle and verb-pair errors
Many JLPT N5 through N3 learners test their Japanese sentences by pasting them into a translation box: if the English translation looks roughly right, they assume the Japanese sentence was natural. Unfortunately, neural translators are built to guess your intended meaning even when your particles are backwards—so “私が先生に褒めました” still translates as “My teacher praised me” even though the Japanese actually says you praised the teacher.
A dedicated Japanese grammar checker judges the Japanese text itself. It checks whether your particle matches the verb’s transitivity, whether a passive or causative-receiving form (-てくれる / -てもらう) points in the right direction, and whether your verb stem matches the suffix attached to it.
Checking te-form chains, adjective inflections, and polite vs. casual mixing
Japanese agglutinates tense, negation, desire, and politeness onto the end of verbs and adjectives. Mixing up Group 1 (godan) and Group 2 (ichidan) te-forms—such as writing 帰て instead of 帰って, or attaching じゃない directly to an い-adjective—is one of the most common hurdles when moving from textbook drills to writing your own sentences.
The checker above uses Japanese word segmentation to highlight only the exact kana or kanji characters that changed, while accepting both polite desu/masu (丁寧語) and casual speech (タメ口) so your personal voice stays intact.
| Japanese Pattern | Learner Draft | Corrected Japanese & Explanation |
|---|---|---|
| Location of action (で) vs. existence/destination (に) Source: wonderglot.com/ja | カフェにコーヒーを飲みました。 | カフェでコーヒーを飲みました。 (Use で for the place where an active event happens; reserve に for existence with ある/いる or movement targets.) |
| Potential & desire objects (が vs. を) | 私は日本語を話せます。 / 水を飲むたいです。 | 私は日本語が話せます。 / 水を飲みたいです。 (Attach たい to the ます-stem 飲み; potential verbs like 話せる typically mark the ability target with が.) |
| Transitive vs. intransitive pairs (他動詞・自動詞) | 電気を消えてください。 | 電気を消してください。 (消える is intransitive “goes off”; turning something off with を requires transitive 消す → 消してください.) |
| い-adjective vs. な-adjective inflection | この部屋は静かいです。 / 楽しいだった。 | この部屋は静かです。 / 楽しかった。 (静か is a な-adjective and takes no い; 楽しい conjugates its past tense directly to 楽しかった.) |
| Giving & receiving verbs (あげる・くれる・もらう) | 友達は私に本をあげました。 | 友達は私に本をくれました。 (When someone gives something to you or your in-group, Japanese uses くれる rather than あげる.) |
Combining grammar checks with Japanese reading practice and story dialogue
Checking a sentence in isolation solves today’s question, while using that grammar inside an unfolding story builds long-term intuition. On Wonderglot, you get Japanese reading practice with clickable word boundaries and furigana above kanji, and every time you reply to a character, this same grammar judge quietly notes any particle or conjugation slip beneath your turn.
Every free Wonderglot account includes free messages every day with Japanese grammar feedback, a writing helper, and permanently free dictionary word lookups, with Wonderglot Plus at US$8.99/month or US$59.99/year.
Common questions
- Does this Japanese grammar checker explain particle choices like は vs. が and に vs. で?
- Yes. When a particle makes a sentence unnatural or changes its meaning, the checker swaps only that particle and explains why the verb or context calls for は, が, を, に, で, or へ.
- Does it accept both polite (です・ます) and casual Japanese sentences?
- Yes. The checker does not force casual sentences into textbook です・ます form; it only corrects genuine grammar, conjugation, particle, or kanji/kana spelling errors.
- Can I check Japanese sentences while practicing conversation?
- Yes. Inside Wonderglot’s Japanese stories on /ja, every typed or spoken reply you send can receive this exact character-level diff and English explanation while the character responds to your line.
- Is the Japanese grammar checker free?
- Yes. You can check Japanese sentences on this page for free, and every free Wonderglot account includes free messages every day with all Japanese learning tools plus permanently free dictionary lookups. Plus is US$8.99/month or US$59.99/year.
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