Compare AI text detectors, pricing and stated accuracy
Compare the best AI detection tools for writers, publishers and schools. Each row shows free access, pricing, limits and the accuracy claim stated by the vendor.
The fact matrix
Read each row as a plan summary, then check the stated limits and vendor claim before choosing. Under each cell is the vendor page we read and the date. The order of the rows is not a ranking.
| Tool | Free plan | Price | Stated limits | Vendor's accuracy claim |
|---|---|---|---|---|
| GPTZeroGPTZero | Yes. Text can be scanned without paying; a free account is needed for scans over 10,000 characters. gptzero.me checked 2 Oct 2026 | Not verified Not verified in US dollars: the pricing page showed Australian dollars (Premium A$17.99/month list, A$12.59 with a 30% promo, billed annually). gptzero.me tried 2 Oct 2026 | Premium: up to 300,000 words per month. Professional: 500,000 words per month. gptzero.me checked 2 Oct 2026 | The vendor states a 99% accuracy rate; we have not tested this. It also says no AI detector is 100% accurate and results should not be used to punish or as the final verdict. gptzero.me checked 2 Oct 2026 |
| Originality.aiOriginality.ai | Yes. Basic (free, no subscription): AI detection only, 3 scans per day, up to 2,000 words per scan. originality.ai checked 2 Oct 2026 | Pro: US$14.95/month billed monthly, or US$12.95/month billed yearly (US$155.40 a year). The page states all prices are in USD. originality.ai checked 2 Oct 2026 | Pro: 2,000 credits per month, expiring monthly; 1 credit covers 100 words of AI checking. originality.ai checked 2 Oct 2026 | The vendor states 97.8% overall accuracy for its multilingual model; we have not tested this. It also says shorter text may affect accuracy and sets a 100-word minimum. originality.ai checked 2 Oct 2026 |
| Copyleaks AI DetectorCopyleaks | Yes. The vendor says up to 25,000 characters per scan can be checked free without logging in; a free account adds monthly credits. copyleaks.com checked 2 Oct 2026 | Personal: $167.88 billed annually (shown as $13.99/month). Shown with a $ sign; the page did not label the currency. copyleaks.com checked 2 Oct 2026 | Personal: 1,200 unified credits, enough to scan up to 300,000 words or 1,200 images. copyleaks.com checked 2 Oct 2026 | The vendor states over 99% accuracy and a .03% false positive rate; we have not tested this. No caution about relying on results was stated on the pages we read. copyleaks.com checked 2 Oct 2026 |
| Turnitin AI writing detectionTurnitin | Not verified Not verified: no free plan is mentioned on the page we read. turnitin.com tried 2 Oct 2026 | Not verified Not verified: no price is published on the page. The vendor says the AI detection capability is available with its Originality product, and the page links to Contact Sales. turnitin.com tried 2 Oct 2026 | The vendor refers to a 300-word count requirement for documents in its false positive testing. turnitin.com checked 2 Oct 2026 | The vendor states false positive rates of 0.014 for English language learners and 0.013 for native English writers on documents of 300+ words; we have not tested this. turnitin.com checked 2 Oct 2026 |
| QuillBot AI DetectorQuillBot | Yes. Free use covers up to 1,200 words per scan with limited explainer cards. quillbot.com checked 2 Oct 2026 | Not verified Not verified: the detector page names a Premium tier but shows no price, and the Premium page showed a bot challenge. quillbot.com tried 2 Oct 2026 | Free: up to 1,200 words per scan; at least 80 words are needed to scan. Premium: no word limit and unlimited scans. quillbot.com checked 2 Oct 2026 | The vendor cites a 99% detection rate from independent evaluations; we have not tested this. It also says no detector is 100% accurate and never to rely on AI detection alone for decisions. quillbot.com checked 2 Oct 2026 |
| Grammarly AI DetectorGrammarly | Yes. The vendor offers a free AI detector on its page that shows what percentage of the text appears AI-generated. grammarly.com checked 2 Oct 2026 | Grammarly Pro is listed at US$12 with a 7-day free trial; the billing term was not shown in the text we read. Pro includes plagiarism and AI text detection. grammarly.com checked 2 Oct 2026 | Not verified Not verified: no word or scan limit for the free detector is stated on the pages we read. grammarly.com tried 2 Oct 2026 | The vendor states 99% detection accuracy; we have not tested this. It also says no AI detector is 100% accurate and results should never be relied on alone. grammarly.com checked 2 Oct 2026 |
| Winston AIWinston AI | A free tier is listed as a 14-day trial with 2,000 credits. gowinston.ai checked 2 Oct 2026 | Essential: listed at $18/month on monthly billing, or $10/month on annual billing; the page also shows a 50% coupon. Shown with a $ sign; the page did not label the currency. gowinston.ai checked 2 Oct 2026 | Free trial: 2,000 credits. Essential: 100,000 credits per month. gowinston.ai checked 2 Oct 2026 | The vendor states 99.87% overall accuracy from its own in-house evaluation on 12,000 English documents; we have not tested this. No caution about relying on results was stated on the pages we read. gowinston.ai checked 2 Oct 2026 |
| ZeroGPTZeroGPT | Yes. A free tier is listed at $0 forever with no credit card needed. zerogpt.com checked 2 Oct 2026 | Not verified Not verified in US dollars: the pricing page showed Australian dollars (PRO A$19.99/month, or A$155.88 a year on annual billing). zerogpt.com tried 2 Oct 2026 | Free: 15,000 characters per AI detection. PRO: 100,000 characters per detection and 50 batch files. zerogpt.com checked 2 Oct 2026 | The vendor states 98.4% detection accuracy and a false positive rate under 1%; we have not tested this. No caution about relying on results was stated on the pages we read. zerogpt.com checked 2 Oct 2026 |
Scroll the table sideways to see every column.
About the prices. Vendor pages were read on 1 and 2 October 2026 from a connection in Australia. Where a vendor shows local prices, we took the US-dollar figure from its United States page or its help centre and link to that page. Where we could not read a US-dollar price, the cell says so and names the currency we saw. Prices in other countries can differ.
Who each one suits, and who it does not
These lines are drawn only from the facts we could read on vendor pages. We have not run our own tests, so nothing here ranks the tools on the quality of their output.
GPTZeroSource: gptzero.me
- Best for
- People who want to try detection without paying first and may later need a monthly allowance in the hundreds of thousands of words.Based on: free plan, stated limits
- Not ideal for
- Anyone who wants a single result to settle a dispute, since the vendor itself says results should not be the final verdict.Based on: vendor's accuracy claim
Originality.aiSource: originality.ai
- Best for
- Publishers and small teams who want a credit-based plan with site scans and team management.Based on: stated limits, listed features
- Not ideal for
- People who need more than a few free scans a day or want to check very short passages.Based on: free plan, vendor's accuracy claim
Copyleaks AI DetectorSource: copyleaks.com
- Best for
- People who want AI and plagiarism checks in one report, or a quick free check of a long passage without logging in.Based on: free plan, listed features
- Not ideal for
- Buyers who want to pay month to month at the listed price, as the figure we read is billed annually.Based on: price
Turnitin AI writing detectionSource: turnitin.com
- Best for
- Schools and universities that already run submissions through an LMS and Turnitin similarity checking.Based on: listed features, price
- Not ideal for
- Individuals who want to check a document themselves, since no public price or free plan is shown.Based on: free plan, price
QuillBot AI DetectorSource: quillbot.com
- Best for
- People who want a free check of a shorter document, up to 1,200 words per scan.Based on: free plan, stated limits
- Not ideal for
- Checking long documents on the free tier, or very short passages under 80 words.Based on: stated limits
Grammarly AI DetectorSource: grammarly.com
- Best for
- Writers who want a free check plus explanations and rewrite help inside a wider writing tool.Based on: free plan, listed features
- Not ideal for
- People who need stated scan limits up front, or a standalone verdict, which the vendor says no detector can give.Based on: stated limits, vendor's accuracy claim
Winston AISource: gowinston.ai
- Best for
- People who want text, image and document checks under one monthly credit allowance.Based on: listed features, stated limits
- Not ideal for
- Anyone wanting an ongoing free plan, as the free tier is described as a 14-day trial.Based on: free plan
ZeroGPTSource: zerogpt.com
- Best for
- People who want a free check of up to 15,000 characters and a bundle of other writing tools.Based on: free plan, stated limits, listed features
- Not ideal for
- Readers who need a confirmed US-dollar subscription price before choosing, which we could not read.Based on: price
How to choose from this table
Start with the access you need. GPTZero offers free scans, with a free account needed for scans over 10,000 characters. QuillBot covers up to 1,200 words per free scan, while ZeroGPT allows 15,000 characters per free AI detection.
Check the billing term before you budget. Originality.ai lists Pro at US$14.95/month billed monthly or US$12.95/month billed yearly. Winston AI lists Essential at $18/month on monthly billing or $10/month on annual billing, but its page did not label the currency.
Compare allowances before submitting long work. GPTZero lists up to 300,000 words per month for Premium. Originality.ai provides 2,000 credits per month, with 1 credit covering 100 words of AI checking, while QuillBot says Premium has no word limit and unlimited scans.
Match the tool to your publishing workflow. Turnitin AI writing detection suits schools and universities already using its similarity checking. Originality.ai fits publishers and small teams wanting site scans and team management, while Winston AI combines text, image and document checks under one credit allowance.
Treat not verified as a reason to check, not a mark against the product. It means the vendor page did not show us the detail on the day. Every figure, with its source and date, is also in the fact ledger.
Related: AI tools compared by task, price and usage limits, Free AI tools and their plan limits.
Questions people ask
Which AI detection tool has a free plan?
GPTZero, Originality.ai, Copyleaks AI Detector, QuillBot AI Detector, Grammarly AI Detector and ZeroGPT all offer free access as described on their vendor pages. Winston AI lists a 14-day trial with 2,000 credits. The Turnitin page did not mention a free plan.
What accuracy claims do the vendors make?
The vendors state claims including 99% for GPTZero, 97.8% overall for Originality.ai, over 99% for Copyleaks and 99% for QuillBot. Turnitin states false positive rates of 0.014 for English language learners and 0.013 for native English writers on documents of 300+ words. AI Select has not tested these claims.
Which detector has the largest stated free allowance?
The table does not establish a ranking because the allowances use different units. Copyleaks says up to 25,000 characters per scan can be checked free without logging in, GPTZero says scans over 10,000 characters need a free account, and ZeroGPT lists 15,000 characters per free AI detection.
Can I see the US-dollar price for every tool?
No. GPTZero and ZeroGPT showed prices in Australian dollars, so their subscription prices were not verified in US dollars. The Turnitin page published no price, and the QuillBot detector page named Premium but did not show a price.