Formal writing can read as machine-written
No detector is always right. A score describes patterns in the writing — it does not show how the text was produced.
Why formal prose gets flagged
Detectors do not read meaning. They measure shape: how much sentence lengths vary, how often a sentence opens the same way as the last one, how wide the vocabulary spread is, how many stock connectives appear. Formal writing is trained toward evenness — consistent sentence length, conventional transitions, a restricted register. Machine writing is even for a different reason. The measurements cannot tell the reasons apart.
Formal, formulaic or second-language writing can be flagged even when a person wrote every word. Rewritten machine text can also pass. Read the highlighted sentences and the reasons given, not just the overall number.
What a score does not prove
If a result matters — a grade, a job, a complaint — treat it as a starting point for a conversation. Drafts, notes and version history are better evidence than any score.
If you have been accused
What actually settles it is how the draft was written — version history, notes, the paragraph you deleted and rewrote.
If you have been wrongly accused →