5 Free AI Text Detectors That Actually Work (2026 Update)

An unreliable AI detector is worse than none: it gives you either false confidence or false panic. So the first thing to say about the five free detectors below is that nobody can tell you which is most accurate, and this page used to pretend otherwise.

What this page used to say, and why it is gone

It published a benchmark. Five detectors, four samples — a passage written by hand, one from ChatGPT, one from Claude, and the ChatGPT one run through a humanizer — and twenty scores in a table. It reported GPTZero at 4% on the human sample, this site's detector at 2% and ZeroGPT at 11% — none of which was measured.

That test was never run, and we cannot run it: GPTZero, Copyleaks, ZeroGPT and Sapling all forbid the automated submission a comparison requires. Somebody else can, and has — see the independent academic comparison below — but it was not us and the numbers in that table were invented. The table also gave this product the best false positive rate in the field, 2%, while our own published measurement is 4.2% with a 95% confidence interval running from 0.7% to 20.2% — a number we had to measure, publish and defend, sitting next to a better one we made up.

It is gone. What follows is the part of the comparison that can be checked by reading each vendor's own page, which is what free tiers are.

What each free tier actually gives you

Allowances change often and are the vendors' to set — check the pricing page before you rely on one. Ours is in the code: FREE_LIMITS.detector in functions/api/tools/_tools.js, unlimited daily uses at a 3,000-word cap, no account.

How to choose without an accuracy ranking

If you check text often, the binding constraint is the cap, not the accuracy. A detector you can only run three times a day is not a detector you can use on a draft you are revising. That is a real, checkable difference and it is the honest reason to prefer an unlimited free tier — ours or ZeroGPT's — over a metered one.

Prefer a tool that shows you which sentences it reacted to. A single percentage cannot be argued with, checked, or learned from. A tool that marks the specific phrases lets you judge whether it has a point. Ours does this on the free tier and documents what it looks for; GPTZero, Copyleaks and Sapling all show some form of per-passage output too.

Run more than one, and treat the lowest score as the informative one. The failure that costs you something is a false positive on your own writing. If one tool flags a passage and three do not, the interesting question is what that one tool is reacting to — not whether you are guilty.

Do not chase a number down. Editing a draft until a detector goes quiet optimises for the detector, not the reader, and the score will not travel: the tool your professor or editor runs is not the tool you ran.

A word on accuracy expectations

Every detector here publishes an accuracy figure about itself. GPTZero publishes considerably more than most — a false positive rate, a recall figure, its corpus size, the models it tested against — and its numbers are far better than ours. An independent academic comparison does exist — Jabarian and Imas (2025, University of Chicago Booth / Becker Friedman Institute, working paper 2025-116), over 1,992 passages — though it covers Pangram, Originality.ai and GPTZero rather than the free tiers listed above. We cannot run our own: the automated submission it needs is against the vendors' terms.

We publish ours because a detector whose failure rate is unknown cannot be used responsibly by anybody:

• False negative rate 96%. Given AI-written text, ours usually does not flag it.
• False positive rate 4.2%, one human sample in 24, 95% CI 0.7%–20.2%.
• ROC-AUC 0.407, where 0.5 is a coin flip.
• The corpus, the code and the caveats: /ai-detector/accuracy.

Those are bad numbers. They are also the only ones on this page that anyone can check, which is the whole argument for reading them.

If you have been accused on the strength of a detector score, what to do about it is a different and more useful page than this one.