22 September 2026 · 2 min read
Why was my own writing flagged as AI?
A detector did not find anything in your text — it guessed from your writing style, and plain, careful prose is what it guesses wrong about.
Because the detector guessed, and it guessed wrong. It did not find anything in your document — it measured how predictable your word choices are and decided that plain, orderly prose looks machine-made.
There is nothing in the text to find
A detector reading plain text has no watermark to read. OpenAI said in 2024 that it had built a text watermarking system for ChatGPT and chose not to turn it on, citing among other things the risk of false accusations against people writing English as a second language. Its own detector, the AI Text Classifier, was withdrawn in July 2023: it caught 26% of AI text while flagging 9% of human text as AI.
What is left is style. Detectors score perplexity — roughly, how surprising each next word is — and burstiness, how much sentence length varies. Low surprise and an even rhythm read as machine. So does an essay written to a rubric by someone being careful.
Who it gets wrong
A 2023 Stanford study in Patterns ran 91 TOEFL essays, all human-written, through seven commercial detectors. Eighteen were flagged by all seven. Eighty-nine of the 91 were flagged by at least one. The same detectors were near-perfect on essays by US eighth-graders. The difference was not who used AI. It was whose English was less idiomatic.
Turnitin publishes a false positive rate under 1% on whole documents. That is its own testing rather than an independent measurement, and it applies to long-form work — Turnitin raised its minimum to 300 words because shorter submissions scored less accurately. Across a term of submissions, 1% is still a queue of people.
What to do with the flag
Ask what it is based on. A percentage is not a finding: there is no hidden mark, no passage anyone can point to and show you. A scan for real artefacts such as invisible characters at least gives you something concrete to look at, though what it finds, or does not find, says nothing about who wrote the text either.
Keep your drafts, comment history and notes. They are the only record of how the work was made.
Check something yourself
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