Japanese AI detector & writing-pattern checker

Japanese AI detector

What the Japanese AI detector does

This app checks Japanese text for the patterns typical of AI-generated Japanese writing: register consistency between desu-masu and da-dearu, full-width punctuation, and stock closing lines like いかがでしたか. It's built for the exact question people search, is this Japanese text AI-written, and answers with a labelled list of signals instead of a bare score.

It runs as a server tool: your text goes to our AI server to be scored, and the flags come back explained. You get 5 free checks in any rolling 24 hours, no account needed.

The real tells

How AI-written Japanese text actually gives itself away

Japanese has its own tells that a checker built around English phrasing would never catch. None of them mean anything alone; the app reads for how many show up together.

The いかがでしたか closing

いかがでしたでしょうか wrapping up a piece that never needed the question, a template so common in AI-generated Japanese blog content that it has its own reputation among readers.

A register that never slips

です・ます kept polite throughout, or だ・である kept plain throughout, with none of the accidental mid-paragraph switching real drafts tend to have.

Suspiciously clean full-width punctuation

、。！？ rendered perfectly full-width throughout, without the stray half-width ASCII punctuation ordinary typing sessions tend to introduce.

No word spacing, plus odd exceptions

Japanese carries no spaces between words. A stray space inserted around an English loanword or after a punctuation mark stands out precisely because the rest of the text has none.

A closing summary paragraph

A tidy wrap-up added to a piece that never asked for one, doing the same job いかがでしたか does even when that exact phrase is avoided.

Workflow

How to run the Japanese AI detector on your own text in three steps

Nothing to configure, no format to match.

1. Paste your Japanese text

A draft, a submission, a comment. A paragraph gives the check enough structure to read.

2. Run the check

The text goes to our AI server once, gets scored, and the flagged patterns come back to the page.

3. Read the flags, not just a score

Each signal ships with a plain-language reason. Use that to decide what the result means for your text.

Straight answer

Can you actually tell which AI wrote Japanese text?

Not for certain. Most models default to a polite, consistent desu-masu register in Japanese regardless of which one wrote it, and several share the same いかがでしたか-style closing habit, so this app reads for machine-written Japanese broadly, not for a single model.

Ask the same model for a plain, literary da-dearu register, or a casual tone, and much of that default shape disappears. Treat a match as worth a closer look, not as a finished answer.

Why flags happen

Why Japanese writers get flagged by mistake

Japanese has solid training data overall, but the writing that reads most like this app's default profile is exactly the writing that has nothing to do with AI.

Keigo-heavy business writing

Formal honorific Japanese in business correspondence already keeps a rigidly consistent polite register, for reasons that predate AI by decades.

Machine-translated Japanese

Japanese translated from English by a separate tool often lands as grammatically correct but stiff, matching this app's default profile.

Careful non-native learners

Desu-masu consistency is exactly what Japanese courses teach as the safe default, so a learner following the lesson closely writes the same shape a model defaults to.

If it happens to you

What to do if your Japanese writing gets wrongly flagged

A flag here is a signal, not a verdict, and formally consistent Japanese overlaps with this app's default profile more than casual writing does.

Keep every draft

Earlier versions are the clearest evidence a piece was built, not generated whole.

Note your intended register

Why you kept desu-masu or da-dearu strictly consistent, for a business or academic context, is something a generic default can't supply.

Ask exactly what was flagged

A named pattern, a closing phrase or a register choice, is something you can discuss. A bare score isn't.

Who it's for

Who uses the Japanese AI detector, and what the free limit is

Editorial teams screening Japanese submissions, teachers weighing in on unusually polished essays, and writers checking their own drafts before sending them out.

5 free checks in any rolling 24 hours, no account required. The window rolls forward rather than resetting on a clock, so five usually covers one submission or one flagged paragraph at a time.