The old version of this page ranked ten AI detectors. We removed that ranking because the tools had not been tested on one shared dataset, several feature claims were already stale, and Turnitin was described as a free public detector when it is licensed through institutions.
This replacement takes a narrower approach. It records which well-known services offered a no-cost browser check or trial on 1 September 2026, then explains how to compare their results. The list is not a performance ranking. Free limits and account requirements can change, so confirm them before planning a large review.
Free access we verified
Detecting AI
Our AI detector accepts text in the browser and returns document and sentence-level signals. The result is meant to guide a closer review. It does not identify a writer or prove misconduct.
GPTZero
GPTZero offered a free web scan, with a free account available for larger texts and additional document handling. Its report included an overall classification and sentence highlighting. GPTZero is a competitor. We include the name because readers search for it, not because we endorse its marketing claims.
Copyleaks
Copyleaks offered a public text scan and additional detail through an account. Its public material described an overall result and more detailed passage information for signed-in users. Treat its advertised accuracy figures as provider claims unless you reproduce the named test.
Grammarly
Grammarly provided a free browser scan that reports how much of the submitted text resembles AI-generated writing. Its own explanation says the result cannot establish a definitive conclusion. That limitation is useful and should remain visible in any review.
QuillBot
QuillBot offered a free AI detector with per-scan and daily limits. The report separated categories of writing and supplied explanations for flagged text. It also sells rewriting products, so a reviewer should keep detection evidence separate from advice designed to change a score.
Scribbr
Scribbr offered a no-sign-up detector with a word limit per submission. Its free and premium detectors did not have identical model coverage. Check which version produced a result before comparing it with another service.
Sapling
Sapling offered a free public detector for shorter passages and a larger allowance for paid users. Its page explicitly warned that false positives and false negatives occur and that no detector should be used as a standalone authorship decision.
Originality.ai
Originality.ai offered a small number of free daily scans at the time of this review. Its commercial product and public checker may not expose the same settings or report depth. Record which interface you used.
Winston AI
Winston AI offered a free trial without a credit card. A trial is not the same as an indefinitely free checker, so compare the usable allowance and the report you receive rather than the wording on a sign-up button.
What about Turnitin?
Turnitin did not provide a public free AI-writing detector. Access depended on an institution licensing and enabling the feature. A website claiming to provide a free Turnitin AI score is not necessarily using Turnitin. Do not upload student work to an unknown copycat service.
How to make a fair comparison
- Use the same text. Keep headings, quotations, references, and formatting consistent. A changed input is a changed test.
- Choose substantial samples. A short answer or a few sentences usually provide weak evidence. Test prose long enough for the tool to analyze a pattern.
- Prepare known examples. Include human writing with a documented history and generated writing whose model and prompt you recorded. Do not judge a detector only on one convenient sample.
- Define an error before testing. A false positive and a false negative have different costs. In education, a false accusation can be more serious than a missed flag.
- Record the date and version. Detector models and thresholds change. A result is a snapshot, not a permanent fact about the document.
- Compare the meaning of each score. One number may estimate model confidence while another describes the share of highlighted text. Equal numbers may answer different questions.
- Inspect the passages. A report with useful sentence evidence is easier to review than a single unexplained percentage.
- Check privacy before uploading. Student work, unpublished manuscripts, and client documents may contain personal or confidential information. A free price does not answer how a service stores or uses the text.
There is no permanent best detector
Research benchmarks show why a fixed ranking ages badly. Detector performance changes across domains, models, decoding settings, edits, and attacks. A tool that performs well on long English essays may behave differently on short answers, translated prose, or a new generation model. Provider accuracy claims are not interchangeable when the test sets and thresholds differ.
For an individual review, use a detector to locate evidence, then check drafts, sources, version history, policy, and the writer's explanation. For procurement, run a documented evaluation on the languages and writing types your organization actually handles. The Detecting AI methodology explains how we present our own signals and their limits.