detection
Best Free AI Detector
The best free AI detectors ranked on independent accuracy tests: Pangram, GPTZero, Copyleaks and ZeroGPT, with how much each lets you check for free, whether you need an account, and why no free checker is proof of AI use.
Quick answer: The best free AI detector for most people is Pangram’s free plan, because Pangram has the strongest independent results of any detector: it was the only tool to keep false positives at or below 0.5% while still catching AI text in a University of Chicago Booth study (Chicago Booth Review), and the only one of four to detect fully AI-written papers in a peer-reviewed June 2026 study (Van Vlasselaer et al.). Pangram’s free plan covers up to 2,000 words a day (Pangram). For a quick check with no account, GPTZero, because its free checker runs without signing up and classified every human paper correctly in the same peer-reviewed study. For the longest free check, Copyleaks, because it scans up to 25,000 characters without an account. The caveat: every free detector misses AI text that has been edited or run through a humaniser, and none is accurate enough to prove that someone used AI.
The current state of free AI detection
Most of the leading detectors have a free tier, limited by a daily or monthly word allowance, a cap on each check, or fewer explanations of the score. The independent studies test each company’s detector rather than its free plan specifically, so the results below describe the detector behind each free checker.
The independent evidence is clearer than it was. A peer-reviewed study published on 29 June 2026 in the International Journal for Educational Integrity tested Turnitin, GPTZero, Copyleaks and Pangram on 160 long academic papers. The authors report all four correctly identified the human-written papers, but on fully AI-written papers Pangram averaged 85.7% AI while GPTZero and Copyleaks averaged about 14% (Van Vlasselaer et al.). A University of Chicago Booth study by Jabarian and Imas found Pangram was the only detector to hold false positives at or below 0.5% while still detecting AI text reliably (Chicago Booth Review).
Free checkers fail in the same places paid ones do. The RAID benchmark, published at ACL 2024 with more than 6 million generations across 11 models, found that detectors are “easily fooled” by paraphrasing, changes in sampling and models they have not seen (RAID). Text that has been edited, paraphrased or passed through a humaniser is where every detector, free or paid, is weakest.
The vendors’ own numbers are a ceiling. All four ranked detectors advertise 98% accuracy or more (Pangram 99.8%, GPTZero and Copyleaks 99%, ZeroGPT 98.4%), measured on clean, unedited AI text. Independent tests on mixed and edited text come in lower, sometimes by 20 to 30 points. This page ranks on the independent figures and labels the vendors’ claims as theirs.
Top free AI detectors compared
Ranked on how well each free checker does the most common job: telling AI text from human text without wrongly flagging a person. False-positive control counts most, then detection, then how much you can check for free.
| # | Free detector | Free allowance | Account needed | Independent evidence | Best for |
|---|---|---|---|---|---|
| 1 | Pangram | Up to 2,000 words a day, plus 3 image scans | No, for the homepage checker | Only detector to meet a 0.5% false-positive cap (Chicago Booth); only one of four to detect fully AI papers (IJEI 2026) | The most accurate free check |
| 2 | GPTZero | Basic scan without an account; higher limits with a free account | No, for a basic scan | Every human paper classified correctly, but 0% on fully AI papers and 2.5% on humanised ones (IJEI 2026) | A quick check with no sign-up |
| 3 | Copyleaks | Up to 25,000 characters a scan; monthly credits with a free account | No | Every human paper classified correctly; 30.0% on hybrid and 22.5% on humanised papers, 0% on fully AI papers (IJEI 2026) | The longest free check |
| 4 | ZeroGPT | Up to 15,000 characters a check | No | 64.35% accuracy and a 16.67% false-positive rate on journal abstracts (Pratama, 2025) | A rough first look only |
“IJEI 2026” is the peer-reviewed study in the International Journal for Educational Integrity by Van Vlasselaer, Van Droogenbroeck and Spruyt. Its AI texts were generated in May 2025, and every vendor has shipped model updates since, including Pangram 4 in July 2026 and GPTZero 4o in September 2026.
The best free AI detectors in detail
1. Pangram: the most accurate free check
Free plan: 20 credits a day, covering up to 2,000 words (one credit is 100 words, rounded up), plus 3 image scans a day in research preview; credits refresh daily (Pangram). Tom’s Guide reports that the checker on Pangram’s homepage runs without logging in (Tom’s Guide) Paid plans: Individual $20 a month for 300,000 words; Professional $65 a month with five times the words and $200 a month in API credits (Pangram)
Pangram has the best independent record of any AI detector. In the University of Chicago Booth study it was the only tool to satisfy a false-positive cap of 0.5% or lower without losing the ability to detect AI text (Chicago Booth Review). In the June 2026 peer-reviewed study it averaged 85.7% AI on fully AI-written academic papers, where the other three tools averaged 14.3% or less, and 45.5% on hybrid papers whose actual AI share was 46.3% (Van Vlasselaer et al.). Pangram advertises 99.8% accuracy or more; that is its own figure, measured on clean text. Pangram 4, released on 29 July 2026, targets mixed human and AI text and humaniser output.
Where it falls short: 2,000 words a day covers one long essay or a few short pieces, not a class set of submissions. The independent studies tested Pangram’s detector, not its free plan specifically.
2. GPTZero: the best free check with no sign-up
Free checker: a basic scan at gptzero.me with no account; GPTZero’s FAQ says a free account unlocks larger limits, and the free detector returns confidence scores, AI vocabulary and sentence-by-sentence highlighting (GPTZero). GPTZero does not show its free monthly word allowance on its pricing page. Paid plans: Premium (300,000 words a month) and Professional (500,000 words a month), priced in the visitor’s local currency on GPTZero’s pricing page
GPTZero is the most widely used detector aimed at education. In the June 2026 peer-reviewed study the authors report it correctly identified the human-written papers, which is the property that matters most for a free self-check, while its average AI score on fully AI-written papers was 14.3% (Van Vlasselaer et al.). GPTZero claims 99% accuracy, and says its 4o model, released on 24 September 2026, produced one false positive in 10,402 student essays (GPTZero); the independent results predate 4o. Superhuman, the company formerly named Grammarly, announced a deal to acquire GPTZero on 23 June 2026 (BusinessWire). It said on 30 September 2026 that GPTZero “is now part of Superhuman” (Superhuman).
Where it falls short: GPTZero’s own FAQ says its classifier “is not trained to identify AI-generated text after it has been heavily modified” (GPTZero), and its weak detection of AI-written papers in the 2026 study means a “human” result is weak evidence.
3. Copyleaks: the longest free check
Free scan: up to 25,000 characters without an account; a free account adds monthly scan credits (Copyleaks) Paid plans: from about $10 a month billed annually, with enterprise and API pricing above (see best AI detector)
Copyleaks sells AI and plagiarism detection to schools, universities and businesses, and its free web scan is the most generous of the major detectors by length. In the June 2026 peer-reviewed study the authors report it correctly identified every human paper, and its average AI score on fully AI-written papers was 14.0% (Van Vlasselaer et al.). Copyleaks advertises over 99% accuracy, and its published test of its current V11 model reports a 0.30% false-positive rate at the default setting (Copyleaks testing methodology; see our Copyleaks guide).
Where it falls short: Copyleaks returns a score on text as short as 255 characters, about 40 words, far shorter than anything its accuracy figures were measured on, so short scans are the least reliable. Detection of fully AI-written text was poor in the 2026 study.
4. ZeroGPT: free and popular, but the weakest evidence
Free checker: up to 15,000 characters a check, with no account and a Free plan listed at “$0 forever” (ZeroGPT)
ZeroGPT is among the most-used free detectors because of its no-signup interface. ZeroGPT claims 98.4% accuracy. Independent results are lower and mixed: Pratama’s 2025 study in PeerJ Computer Science put its accuracy on journal abstracts at 64.35%, with a 16.67% false-positive rate and a 45.15% false-negative rate (Pratama), while Cheng and colleagues found in November 2025 that it returned 1.6% to 6.5% AI content on human-written text (Cheng et al.). Weber-Wulff and colleagues found in 2023 that none of the 14 detectors they tested, ZeroGPT included, exceeded 80% accuracy (Weber-Wulff et al.). ZeroGPT is a different product from a different company than GPTZero.
Where it falls short: the 16.67% false-positive rate in Pratama’s 2025 study means roughly one human-written text in six was flagged. ZeroGPT was not among the tools in the June 2026 peer-reviewed study.
How much you can check for free
| Detector | Free limit | Account needed | Paid plan if you outgrow it |
|---|---|---|---|
| Pangram | Up to 2,000 words a day | No, for the homepage checker (Tom’s Guide) | $20 a month |
| GPTZero | Basic scan; higher limits with a free account | No, for a basic scan | Premium, local-currency pricing |
| Copyleaks | Up to 25,000 characters a scan | No | From about $10 a month (annual) |
| ZeroGPT | Up to 15,000 characters a check | No | Paid plans on ZeroGPT’s site |
| QuillBot | Up to 1,200 words a scan, up to 6 scans a day | Not for a basic scan | QuillBot Premium |
| Scribbr | Up to 1,200 words a check | No | Premium check included with a $19.95–$39.95 plagiarism check |
| Grammarly | A basic scan returning one percentage | No | AI Detector agent on paid plans |
QuillBot’s limits are as listed on its AI Content Detector page; Scribbr’s free limit is as shown on its detector page, and its premium terms are from Scribbr’s own 2026 detector guide.
Other tools worth knowing (not ranked)
These free checkers are widely used, but there isn’t yet enough independent assessment of them to rank them.
- QuillBot and Scribbr share the same detection engine, according to Scribbr, and both are free up to 1,200 words a check. Scribbr’s own comparison scored both free checkers at 78%; Scribbr sells a detector, so that is a vendor-run test (Scribbr).
- Grammarly’s free checker needs no sign-up for a basic scan and returns a single percentage. Grammarly says its model is “optimized to minimize false positives”, so by design it misses more AI text. Its “#1 on RAID” claim refers to its paid AI Detector agent, and the predictions behind that ranking were produced by Grammarly itself (see our Grammarly guide).
Detectors that aren’t really free
- Originality.ai has no genuine free tier, only a small allowance of credits at sign-up; its paid plans start at $14.95 a month. It is the strongest detector on paraphrased text in the RAID benchmark (see best AI detector).
- Winston AI offers a trial rather than a free plan.
- Turnitin is sold only to institutions, so individuals cannot run a free check against it, and no free detector predicts what Turnitin will say.
Best free AI detector by use case
- Most accurate free check: Pangram, up to 2,000 words a day, with the best independent results on false positives and detection.
- A quick check with no account: GPTZero, which classified every human paper correctly in the 2026 peer-reviewed study.
- The longest free check: Copyleaks, up to 25,000 characters with no account.
- Checking your own essay before you submit: Pangram or GPTZero, to see whether your own writing gets wrongly flagged; keep drafts and version history as evidence either way.
- Teachers: use a free check as a prompt for a conversation, never as evidence; see AI detectors for teachers.
- Images: Pangram’s free plan includes 3 image scans a day in research preview; for dedicated tools, see best AI image detectors.
The false-positive problem with free checkers
A free detector costs nothing to run, which makes it easy to run often and easy to over-trust. Two findings set the limits. A 2023 Stanford study found that seven detectors flagged a mean of 61.22% of TOEFL essays by non-native English speakers as AI-generated, against about 5% of essays by US eighth-graders (Stanford HAI). The June 2026 peer-reviewed study, whose human papers were written by non-native English-speaking graduate students, found no misclassified human papers across the four tools it tested (Van Vlasselaer et al.), so the newer tools have improved. At ZeroGPT’s 16.67% false-positive rate in the Pratama study, a teacher checking 30 essays would expect about five human-written essays to be flagged. A detector score can start a conversation; it cannot settle one. For the full evidence, see the false-positive problem and how AI detectors work.
Recent developments
- GPTZero 4o (24 September 2026). GPTZero’s new model adds AI Patterns, which names the stylistic features behind a score, and claims one false positive in 10,402 student essays (GPTZero).
- Pangram 4 (29 July 2026). Aimed at mixed human and AI text and humaniser output, released alongside a research preview of image detection (Pangram).
- The peer-reviewed study of four detectors (29 June 2026). Van Vlasselaer, Van Droogenbroeck and Spruyt found only Pangram detected fully AI-written academic papers, and no tool misclassified a human paper (Van Vlasselaer et al.).
- Superhuman agreed to buy GPTZero (23 June 2026). The company formerly named Grammarly announced the deal, which would put GPTZero alongside Grammarly’s own free checker (BusinessWire).
Frequently asked questions
What is the best free AI detector?
Pangram’s free plan is the best free AI detector, because Pangram has the strongest independent results: it was the only detector to keep false positives at or below 0.5% while still catching AI text in a University of Chicago Booth study, and the only one of four to detect fully AI-written papers in a June 2026 peer-reviewed study. The free plan covers up to 2,000 words a day. GPTZero is the best free option with no account, and Copyleaks allows the longest free scan, at 25,000 characters.
What is the most accurate free AI detector?
Pangram is the most accurate on independent evidence. In the June 2026 study in the International Journal for Educational Integrity it averaged 85.7% AI on fully AI-written papers, where GPTZero, Copyleaks and Turnitin averaged 14.3% or less, and the authors report it correctly identified every human paper. Vendor accuracy claims of 98% or more, Pangram’s included, are measured on clean, unedited text.
Is GPTZero free?
Yes. GPTZero runs a basic scan at gptzero.me with no account, and its FAQ says a free account unlocks larger limits. The free detector returns confidence scores, AI vocabulary and sentence-by-sentence highlighting. GPTZero’s paid plans, Premium and Professional, cover 300,000 and 500,000 words a month.
Is ZeroGPT accurate?
ZeroGPT claims 98.4% accuracy, but independent studies are lower. Pratama’s 2025 study in PeerJ Computer Science found 64.35% accuracy on journal abstracts with a 16.67% false-positive rate, so about one human-written text in six was wrongly flagged. A November 2025 study by Cheng and colleagues was more favourable on human text, at 1.6% to 6.5% AI detected. ZeroGPT is free for up to 15,000 characters a check with no account.
Which free AI detector needs no sign-up?
GPTZero, Copyleaks (up to 25,000 characters), ZeroGPT (up to 15,000 characters), Scribbr (up to 1,200 words) and Grammarly all run a basic free check without an account.
Can free AI detectors detect ChatGPT, Claude and Gemini?
They return a score for text from any model, and on unedited output from current models the better detectors flag a substantial share of it. The independent studies used older model output, though: the RAID benchmark contains no Claude or Gemini text and nothing newer than GPT-4, and the June 2026 study’s fully AI papers were written with GPT-4o Deep Research. Edited or humanised text from any model is much harder for every detector.
Is there a free version of Turnitin?
No. Turnitin is sold only to schools and universities, so students cannot check their work against it, and no free detector predicts the score Turnitin will give. See our Turnitin AI detection guide.
Can I check my essay for AI for free?
Yes. Pangram’s free plan covers up to 2,000 words a day and GPTZero runs a free scan with no account. Checking your own work is a sensible precaution against being wrongly flagged, especially if English is your second language. Keep your drafts, notes and version history: they are stronger evidence of your own authorship than any detector score.
Are free AI detectors reliable enough for teachers to use?
Not on their own. Even the best detectors miss edited and humanised AI text, and some flag human writing: ZeroGPT’s false-positive rate was 16.67% in Pratama’s 2025 study in PeerJ Computer Science. Turnitin and GPTZero both say their results should not be the sole basis for action against a student. Use a free score as a reason to talk to a student and look at their drafts, never as proof.
Conclusion: how to choose
Start with what you need to check and what a wrong answer would cost. For the most accurate free check, use Pangram’s free plan, up to 2,000 words a day. For a quick scan with no account, use GPTZero. For a long document in one go, use Copyleaks, up to 25,000 characters. Treat ZeroGPT as a rough first look only. Whatever you use, a free detector gives a probability, not a verdict. If you need more than free allowances cover, or a detector for publishing or enterprise work, see best AI detector; to understand the scores, see how AI detectors work.