Free AI detector and humanizer tools

The table lists every tool on this site whose vendor offers both a humanizer with a free tier or trial and its own AI checker, ordered by the largest free humanizer input, largest first. A tier renews; a trial is a one-time allowance. The last column records what the vendor states about its own checker, in the vendor's words. Plan facts were checked on 8 November 2026 for the first six and on 9 November 2026 for the rest.

Two vendors that sell both sit outside the table above. Phrasly's humanizer page states a free, unlimited AI checker and one free humanization a day of up to 500 words with no sign-up, read 9 November 2026, which makes the pair free for one passage a day; its paid access is a $2 three-day trial or the Unlimited plan, and its review carries the plan facts. Ryne AI's free Amethyst plan humanizes 250 words a run, but its AI Report is a $3.99 purchase, read 9 November 2026, so the pair is not free. The free humanizers without a checker are set side by side on the free humanizer page.

Because the same company built both halves. A humanizer vendor can tune its rewrite against its own checker until the checker says human, and nothing outside the company has tested either half. None of the 11 vendors above publishes a dataset, a date or an outside audit for its built-in checker. Grammarly is the only one that puts a number on it, and the number is Grammarly's claim about a benchmark, with no date for the run on the page read on 9 November 2026. WriteHuman's detector page is the most candid, stating that no detector on the market is fully accurate.

The second problem is structural. Monica's humanizer page says its checker combines GPTZero, Copyleaks and ZeroGPT (Monica AI Humanizer page, read 9 November 2026), and Undetectable AI's homepage says its checker analyses text the way a detector would, read 9 November 2026, beside a 250-word trial stated on its pricing page, checked on 8 November 2026. Neither vendor says whether the checker calls those detectors' own services or imitates them, and a reading from an imitation is a reading from the vendor's model with another company's name on it.

The peer-reviewed record shows why an outside reading is the one that counts, and why even that reading needs a date. Weber-Wulff and colleagues tested 12 public detectors plus Turnitin and PlagiarismCheck on 54 documents and found all 14 below 80 percent accuracy, with the tools disagreeing on the same texts and accuracy falling further on paraphrased text (Weber-Wulff et al. 2023, International Journal for Educational Integrity, read 9 November 2026). A built-in checker adds a fifteenth model to that spread, with no published figures at all.

Detector makers have answered since. GPTZero states that its model shields against common evasion methods, paraphrasing among them, and holds its false positive rate at no more than 1 percent when evaluating AI against human text (GPTZero technology page, read 9 November 2026). That is a vendor figure on vendor data, which is why this site records each detector's own label on the run date rather than quoting a rate. The guide on whether AI detectors work sets the studies beside the vendor claims in full.

Use the free humanizer for what it is, a rewrite with a stated word cap, and use the built-in checker as a preview rather than a result. Then take the output to a detector the vendor does not own. GPTZero, Copyleaks and ZeroGPT each offer a free check on their own sites, and a reading from one of them, with the date, is the figure worth writing down.

A rewrite that drops a claim or invents one has done damage no checker will report. The guides hub holds the rest of this series, including what detectors measure and why their scores disagree. Anyone writing for a class should read their institution's AI policy first; a humanizer does not make undisclosed AI use acceptable.