Free Japanese AI detector & checker

Japanese AI detector

What the Japanese AI detector does

Paste a passage of Japanese text and this Japanese AI detector checks it 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 returns a labelled list of what it found, not a single unexplained number.

It is a server tool. Your text is sent to our AI server to be scored, and you get 5 free checks in any rolling 24 hours. No account, and nothing you paste is needed again once the result is back.

Japanese writing patterns

How AI-written Japanese text actually differs

Japanese has its own tells, separate from the English phrasing habits most detectors talk about. None of these prove anything alone; the check reads for how many appear 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 Japanese 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, exactly as expected, 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, functioning the same way いかがでしたか does even when that exact phrase is avoided.

How it works

How to check Japanese text for AI writing in three steps

Nothing to configure first, no file to prepare.

Step 1

Paste the Japanese text you want checked. A paragraph gives the check enough to work with.

Step 2

Press Check text. It goes to our AI server once, gets scored, and the flagged patterns return to the page.

Step 3

Read each signal and the reason behind it, then judge for yourself. The detector explains; it does not rule.

Straight answer

Can you tell which AI wrote Japanese text?

Not with certainty. 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 these signals point at machine-written Japanese broadly rather than at any one model.

A prompt asking for a plain, literary da-dearu register, or a casual tone, changes the output enough to blur most of this. Treat a match as a lead worth a closer look, never as a finding on its own.

Why flags happen

Why Japanese writers get flagged by mistake

Japanese has solid training data overall, but the writing that reads most like this detector'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

Text translated from English by a separate tool often lands as grammatically correct but stiff, matching this detector'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 you're flagged

What to do if your Japanese writing is wrongly flagged

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

Keep your drafts

Earlier versions are the plainest evidence a piece grew rather than appeared 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 cannot supply.

Ask what was actually flagged

A named signal, a closing phrase or a register choice, can be discussed. A bare score cannot.

Who uses it

Who uses the Japanese AI detector, and how many free checks you get

Editors screening Japanese submissions, teachers giving a second opinion on unusually polished essays, and writers checking their own drafts before sending them anywhere.

You get 5 free checks in any rolling 24 hours, no account needed. The window rolls forward rather than resetting at a fixed hour, so five is usually enough for one submission, one email or one flagged paragraph at a time.