Free AI detectors compared: what each free version gives you
Short answer
Free AI detectors differ most in how much text they check and how often. On 31 October 2026, Copyleaks let anyone check up to 25,000 characters without logging in, Scribbr and QuillBot allowed 1,200 words per check (Scribbr without a daily limit, QuillBot six a day), GPTZero's free plan covered 10,000 words a month, and Pangram gave 20 checks a day after sign-up.
Free limits say nothing about accuracy, and several vendors' own pages contradict each other about their limits. We list what each vendor's page said on that date, alphabetically and without ranking. For accuracy, look at independent tests.
Free limits at a glance
What each vendor's own page said on 31 October 2026, in alphabetical order. This is not a ranking. "Not stated" means we couldn't find it on the vendor's pages.
| Tool | Free amount per check | How often | Account needed? | Plagiarism check free? | Shows which passages? |
|---|---|---|---|---|---|
| AI Checker Plus | First 300 words | 3 checks a day | No | No (paid plans) | Yes: each passage labeled AI-generated, AI-assisted or human |
| Copyleaks | Up to 25,000 characters | More monthly credits with a free account (amount not stated) | No, for scans up to 25,000 characters | Not stated | Sentence-level detail needs a free account |
| GPTZero | 10,000 characters without an account; 150,000 with a free one | 10,000 words a month | No, up to 10,000 characters | Yes, within the 10,000 words a month | Unclear (see below) |
| Grammarly | 1,400 characters (per Grammarly's blog) | 1 scan, then sign up | No, for one scan | Yes (per Grammarly's blog) | No: a percentage; Pro shows which parts |
| Originality.ai | 100 credits per account (1 credit = 100 words); 100-word minimum | Conflicting on its own pricing page (see below) | No, for a free scan | Listed in the free plan | "Sentence level" results listed |
| Pangram | Not stated | 20 checks a day | Yes | No (subscription) | Yes, highlights AI-edited segments |
| QuillBot | 1,200 words; 80-word minimum | 6 scans a day | Not stated | Listed among free tools (scope not stated) | 1 free explainer card |
| Sapling | First 2,000 characters | Not stated | Not stated | No plagiarism checker found | Yes, a score per sentence |
| Scribbr | 1,200 words | Unlimited | No | Overview free; full report $19.95 to $39.95 per document | Section-by-section feedback |
| Undetectable AI | Up to 10,000 words (input counter) | Not stated | No | Not stated | Not stated |
| Winston AI | 2,000 credits in total (AI detection costs 1 credit per word) | 14-day trial | Yes | Not stated (advanced plagiarism detection is a paid plan) | Not stated |
| ZeroGPT | First 15,000 characters shown | Not stated | Not stated (its $0 plan needs sign-up) | Not stated | Yes, highlights sentences it judges AI-written |
Writer.com's free AI detector is gone: on 31 October 2026, its old address redirected to Writer's homepage, which no longer has a detector.
What should you know before trusting these limits?
- Characters aren't words. Some tools count characters and others count words. A limit of 2,000 characters holds far fewer words than a limit of 2,000 words.
- Vendors contradict themselves. Originality.ai's pricing page offers "10K words (100 credits one time)" for the free plan, while a table on the same page says "60 (3 scans/day)." Copyleaks' own page says 25,000 characters per scan without logging in; Grammarly's comparison says 25,000 characters per month. GPTZero advertises sentence-by-sentence highlighting without saying which plan includes it, while Grammarly's blog says that detail is paywalled.
- Ownership. Superhuman, the company formerly known as Grammarly, agreed to buy GPTZero in June 2026. Grammarly's own comparison discloses this.
- Humanizers. ZeroGPT, QuillBot, Grammarly and Undetectable AI also sell tools that rewrite AI text so it reads as human. Undetectable AI markets its humanizer as "scoring as human on every major detector."
- Scribbr's own advice. Scribbr says its free detector handles "GPT2, GPT3, and GPT3.5 with average accuracy" and points readers to QuillBot's detector as "more advance and reliable."
Which free detector fits what you need?
| You want | Free options (31 October 2026) |
|---|---|
| One long check without an account | Copyleaks (25,000 characters), GPTZero (10,000 characters), Undetectable AI (10,000-word counter) |
| Many checks | Scribbr (unlimited, 1,200 words each), Pangram (20 a day, with an account), QuillBot (6 a day) |
| To see which passages look like AI | AI Checker Plus, Pangram, Sapling, ZeroGPT; Copyleaks with a free account |
| A plagiarism check too | GPTZero (within its monthly allowance), Originality.ai (free credits), Grammarly (per its blog), Scribbr (overview only) |
| Your text kept out of AI training | Check each policy. Originality.ai says free-detector text "may be used for training" unless you have an account and opt out. AI Checker Plus never trains on your text and deletes free checks after a day. |
Is a free detector less accurate?
This page compares limits, not accuracy. Accuracy differs a lot between detectors: in Epoch AI's July 2026 test of about 500 human-written passages, Pangram and GPTZero flagged none of them, while Originality.ai flagged 19 (3.8%). No tool is right every time, and short texts are the least reliable. What nine independent studies found and what each tool's score means.
Our interest
We make AI Checker Plus, one of the tools in this table, so we have a stake. Every other row is what that vendor's own page said on 31 October 2026 (two of Grammarly's limits come from its blog), and we haven't ranked anyone. Our free check is smaller than most here, at 300 words; it labels each passage AI-generated, AI-assisted or human-written, and paid plans check up to 5,000 words and add plagiarism checks with sources. Limits change often, so check the vendor's page before you rely on one.
Questions people also ask
What is the best free AI detector?
It depends on what you need. On 31 October 2026, Copyleaks allowed the longest check without an account (25,000 characters), Scribbr allowed unlimited checks of up to 1,200 words, and Pangram allowed 20 checks a day with a free account. Free limits don't measure accuracy, so check independent tests too.
Is GPTZero free?
GPTZero has a free plan that covers up to 10,000 words a month, and checks over 10,000 characters need a free account. GPTZero is now part of Superhuman, the company formerly known as Grammarly, which agreed to buy it in June 2026.
Which free AI detectors work without an account?
On 31 October 2026, Copyleaks (up to 25,000 characters), GPTZero (up to 10,000 characters), Scribbr (1,200 words), Undetectable AI, Originality.ai (a free scan), Grammarly (one scan, per its blog) and AI Checker Plus (300 words, 3 checks a day) all let you check text without signing up. Pangram and Winston AI need an account.
Is it safe to paste private text into a free AI detector?
Read the tool's privacy policy first, especially before pasting someone else's work. Originality.ai says text pasted into its free detector may be used for training unless you have an account and opt out. AI Checker Plus never uses text to train models and deletes free checks after a day.
Sources
- GPTZero: for students (accessed 31 Oct 2026)
- GPTZero: FAQ (accessed 31 Oct 2026)
- GPTZero: Plagiarism Checker (accessed 31 Oct 2026)
- ZeroGPT: pricing (accessed 31 Oct 2026)
- Copyleaks: AI Content Detector (accessed 31 Oct 2026)
- Originality.ai: pricing (accessed 31 Oct 2026)
- Scribbr: AI Detector (accessed 31 Oct 2026)
- Scribbr: Plagiarism Checker (accessed 31 Oct 2026)
- QuillBot: AI Content Detector (accessed 31 Oct 2026)
- Sapling: AI Content Detector (accessed 31 Oct 2026)
- Grammarly: AI Detector (accessed 31 Oct 2026)
- Grammarly blog: best AI detectors (updated 26 Oct 2026)
- Pangram: FAQ (accessed 31 Oct 2026)
- Pangram: pricing (accessed 31 Oct 2026)
- Undetectable AI: AI Detector (accessed 31 Oct 2026)
- Winston AI: pricing (accessed 31 Oct 2026)
- Winston AI: API reference (credits per word)
- Writer.com AI content detector (archived Dec 2024; the live page now redirects)
- SiliconANGLE: Superhuman, formerly Grammarly, agrees to acquire GPTZero (Jun 2026)
- Epoch AI: AI detectors' false negatives (Jul 2026)
- AI Checker Plus: Privacy Policy