An honest instrument for a nervous moment

What this site is

ai-detector.co is a free AI text detector. You paste a passage, the engine measures the statistical patterns that distinguish machine writing from human writing, and you get a reading from 0 to 100 with a plain-English verdict. There is no account system, no stored text and no paid engine behind the free one.

What we believe

The detection market sells certainty it does not have. Accuracy claims of 99% decorate products whose underlying science supports nothing of the kind, and the people hurt by that gap are rarely the buyers: they are students accused on a percentage, applicants filtered by a screening script, writers whose careful prose reads too smooth. Our position is that a detector owes its users the gray zone. The dial here marks scores from 40 to 69 as inconclusive, every verdict carries a note on what it cannot prove, and the site documents the failure modes of the whole field, including ours, in plain language.

How the tool works

The engine reads predictability and uniformity: machine text is smoother than human text in measurable ways. The full explanation, including perplexity, burstiness and why edited AI text defeats every detector, is in how AI detectors work. We publish it because an instrument you cannot interrogate is an instrument you should not trust.

What this tool cannot do

It cannot prove who wrote a text. It cannot tell which AI model produced a passage. It cannot reliably score very short samples, which is why the scan has a 120-character floor. It will sometimes read formal human writing as machine-like and heavily edited machine writing as human, and the verdict copy says so at the moment it matters. Anyone who tells you their detector escapes these limits is describing their marketing, not their model.

Who runs it

ai-detector.co is operated independently. The detector is the product; there are no ads, no affiliate links in our comparisons, and no data resale, since there is no data. For questions, corrections or anything this page should answer and does not, use the contact page.