Best free AI detectors: what each free plan checks (Oct 2026)
6 of the 8 AI detectors we track have a permanent free plan. Every $0 allowance below is quoted from the vendor.
Short answer
Top free plans: GPTZero: 10,000 words per month of basic AI scanning; Undetectable AI: Free with no signup; ZeroGPT: 15,000 characters per AI detection.
- 01GPTZeroFree plan$0
10,000 words per month of basic AI scanning. Upgrade: Premium $23.99/mo.
Try GPTZero (opens in new tab)Affiliate link: we may earn a commission. Disclosure - 02Undetectable AIFree plan$0
Free with no signup. Upgrade: 20K words $19/mo.
Try Undetectable AI (opens in new tab)Affiliate link: we may earn a commission. Disclosure - 03ZeroGPTFree plan$0
15,000 characters per AI detection. Upgrade: Pro $14.99/mo.
Try ZeroGPT (opens in new tab)Official site · zerogpt.com
Vendor-stated, checked . Full ranking, limits and sources below.
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We re-check every vendor's pricing page daily. The weekly digest lists each verified price, limit or free-tier change, with its source.
Free AI detectors
| Tool | Upgrade | Free | Status | What you get for $0 & source |
|---|---|---|---|---|
| Free plans | ||||
01GPTZeroTry GPTZero (opens in new tab)Affiliate link: we may earn a commission |
Cheapest upgrade Premium · $23.99/mo | $0 | Free tier Allowance stated |
Free: 10,000 words per month of basic AI scanning. Source: gptzero.me (opens in new tab) · checked 2026-10-22 |
02Undetectable AITry Undetectable AI (opens in new tab)Affiliate link: we may earn a commission |
Cheapest upgrade 20K words · $19/mo | $0 | Free tier Allowance stated |
Free with no signup; up to 10,000 words per check; the vendor gives no monthly cap. Source: undetectable.ai (opens in new tab) · checked 2026-10-25 |
| Cheapest upgrade Pro · $14.99/mo | $0 | Free tier Allowance stated |
Free forever: 15,000 characters per AI detection. Source: zerogpt.com (opens in new tab) · checked 2026-10-22 | |
| Cheapest upgrade Pro · $14.95/mo | $0 | Free tier Allowance stated |
Free for limited use: the plan card says 10K words (100 credits, one time); the comparison table says 60 credits (3 scans/day), renewing daily. Source: originality.ai (opens in new tab) · checked 2026-10-28 | |
| Cheapest upgrade Pro · $12/mo | $0 | Free tier | Grammarly's AI Detector page says 'It's free'; usage limits are not stated there. Source: grammarly.com (opens in new tab) · checked 2026-10-16 | |
| Cheapest upgrade Premium · $19.95/mo | $0 | Free tier | Free plan includes limited access to the AI Detector; Premium gives full access. Source: quillbot.com (opens in new tab) · checked 2026-10-27 | |
| Trial only | ||||
—Winston AITry Winston AI (opens in new tab)Affiliate link: we may earn a commission |
Cheapest upgrade Essential · $18/mo | — | Trial only | No free plan; 14-day trial with 2,000 credits (about 2,000 words of AI detection at 1 credit per word). Source: gowinston.ai (opens in new tab) · checked 2026-10-25 |
| No free plan listed | ||||
| Cheapest upgrade Personal · $16.99/mo | — | Free tier unclear | No free plan listed; AI detection is included in paid plans. Source: copyleaks.com (opens in new tab) · checked 2026-10-22 | |
Compare the top 4 plans side by side Models, limits, resets and what happens at the cap, in one table.
Who should pick what
- You want the biggest free word allowance: GPTZero. GPTZero's free plan: 10,000 words per month of basic AI scanning. Premium is $23.99/mo month to month or $12.99/mo billed yearly.
- You paste long documents in one go: Undetectable AI / ZeroGPT. Undetectable AI's free detector takes up to 10,000 words per check with no signup. ZeroGPT's free plan: 15,000 characters per AI detection.
- You want a detector, paraphraser and humanizer in one plan: QuillBot. QuillBot: Free plan includes limited access to the AI Detector; Premium gives full access. Premium is $19.95/mo month to month or $8.33/mo billed yearly.
- You already use Grammarly: Grammarly. Grammarly's AI Detector page says 'It's free'; usage limits are not stated there.
- You check content for a team or a publication: Originality.ai / Winston AI / Copyleaks. Originality.ai Pro is $14.95/mo (2,000 credits/month (200K words)). Winston AI has a 14-day trial; Essential is $18/mo month to month or $10/mo billed yearly for 100,000 credits a month. Copyleaks has no free plan listed; Personal is $16.99/mo.
Next steps
How this list is ranked
Free plans that put a number on the allowance (credits, minutes, images, messages) rank first, because you can plan around a number; free plans with unpublished allowances follow. Within each group, order reflects how much each free plan lets you make and use; the note below explains it. Trials and paid-only tools are listed after the ranking so you know they were checked.
Why this order (checked 2026-10-25): GPTZero states a free monthly allowance (10,000 words) on its pricing page. Undetectable AI's detector page says it's free with no signup and takes up to 10,000 words per check, but no monthly cap is stated, and its pricing page says the free trial is limited to 250 words. Because the two pages conflict, it ranks second. ZeroGPT states 15,000 characters (about 2,500 words) per check. Originality.ai's own page gives two different free allowances. Grammarly and QuillBot don't state a number.
Trial, not a free plan: Winston AI's Free tier is a 14-day trial with 2,000 credits, about 2,000 words at 1 credit per word.
We never rank on reviews, affiliate deals or sponsorship. Facts are vendor-stated; "not published" means the vendor doesn't say.
Recent changes in this list
-
limit changeOriginality.ai Pro scan history now listed as 30 Day (was 1 Year)
Originality.ai's pricing page now lists '30 Day Scan History' on the Pro plan card ('$12.95/month' billed yearly, '$14.95/month' monthly, '200K words (2K credits) per month', all unchanged); on 2026-10-27 the same card read '1 Year Scan History'. The page's comparison table listed Pro scan history as '30 days' on both dates, so this may be the card being brought in line with the table rather than a new limit. Enterprise still lists '1 year scan history'.
-
correctionCorrectionQuillBot Premium price corrected to $19.95 (we had listed $23.95)
Our data listed QuillBot Premium at $23.95 a month. QuillBot's Premium page reads '$19.95 USD Per month' in our saved copies from 2026-10-22, 2026-10-23 and 2026-10-27, so we corrected the figure. This fixes our own error; QuillBot did not change its price. The $8.33 billed-annually figure was already correct.
Questions people ask
What is the cheapest AI detector?
Grammarly: Grammarly Pro costs $12/mo. Next cheapest: Originality.ai ($14.95/mo), ZeroGPT ($14.99/mo), Copyleaks ($16.99/mo). Prices checked 2026-10-16.
Which AI detectors have a free plan?
GPTZero, Undetectable AI, ZeroGPT, Originality.ai, Grammarly, QuillBot. Not free: Winston AI (trial only), Copyleaks (none listed).
Which free AI detector tells you exactly what you get?
GPTZero: Free: 10,000 words per month of basic AI scanning.; Undetectable AI: Free with no signup; up to 10,000 words per check; the vendor gives no monthly cap.; ZeroGPT: Free forever: 15,000 characters per AI detection.; Originality.ai: Free for limited use: the plan card says 10K words (100 credits, one time); the comparison table says 60 credits (3 scans/day), renewing daily.
How current is this ranking?
It is rebuilt from our data every time prices are checked; the last check was 2026-10-16. Every price links to the vendor page it came from.