10 Best Free AI Detectors in 2026 (Compared)

The best free AI detector is one that lets you check text without paying, tells you which sentences look AI-written, and is honest that it can be wrong. As of November 2026, HumanizeGo, GPTZero, ZeroGPT and QuillBot give the most useful free checks, while Pangram and Originality.ai offer smaller free allowances on detectors that did well in independent research. No AI detector, free or paid, is right every time.

Free tiers vary more than most people expect. Below we compare 10 free AI detection tools by what the free plan actually gives you, then explain how to pick one.

Disclosure: HumanizeGo is our product. We’ve included it alongside competitors and tried to describe every tool fairly.

Quick picks

• Best overall free AI detector: HumanizeGo, for no-sign-up checks with sentence highlighting and an explanation of the score
• Best for teachers: GPTZero, for color-coded sentence reports and a Google Docs add-on
• Best for long passages without an account: ZeroGPT, at 15,000 characters per check
• Best for QuillBot users: QuillBot AI Detector
• Best for Grammarly users: Grammarly AI Detector
• Best for avoiding false positives: Pangram
• Best for publishers and SEO teams: Originality.ai
• Best for developers: Sapling, with a low-cost metered API
• Best for one-off thesis checks: Scribbr
• Best for AI and plagiarism checks together: Copyleaks

Comparison table

Prices as of November 2026. “Check site” means we couldn’t confirm the current figure on the vendor’s own pages, so look it up before you buy.

Tool	Free plan	Paid from	Best for
HumanizeGo	5 checks/day, 600 words, no sign-up; 20/day, 1,000 words with free account	Detector free; humanizer plans from $7.99/mo	Free checks with explanations
GPTZero	10,000 characters per scan, no account	Check site	Teachers
ZeroGPT	15,000 characters per check, no credit card	Check site	Long passages
QuillBot	Free scans for short texts, daily cap	Check site	QuillBot users
Grammarly	Free scan and file upload	Check site	Grammarly users
Pangram	Free checks after sign-up (terms: check site)	$20/mo	Low false positives
Originality.ai	Small one-time free allowance	$14.95/mo ($12.95/mo yearly)	Publishers, SEO
Sapling	2,000 characters per check	$25/mo ($12/mo yearly)	Developers
Scribbr	Free checks (limits: check site)	Pay per document	Thesis checks
Copyleaks	Limited free use (check site)	Check site	AI + plagiarism

What does a free AI detector actually give you?

Before the list, it helps to know what to compare. Free AI detection tools differ in five ways:

• Text per check. Some count words, others count characters. As a rough guide, 2,000 characters is about 300 to 350 words of English.
• Daily or monthly caps. A big per-check limit means little if you only get a handful of checks.
• Sign-up. Several tools work without an account, others need one for anything beyond a short sample.
• Sentence highlighting. Seeing which sentences triggered the score is far more useful than a single percentage.
• Explanations. A few tools tell you why text looks AI-written.

If you want the theory behind these scores, read how AI detectors work.

The 10 best free AI detectors in 2026

1. HumanizeGo — best free AI detector with explanations

Our free AI detector runs without an account. Guests get 5 checks a day of up to 600 words each, and a free account (email login, no password) raises that to 20 checks a day of up to 1,000 words. Each result shows an overall AI percentage, highlights every sentence, lists the signals that drove the score and adds writing stats such as burstiness and vocabulary diversity. If your own draft gets flagged, you can revise those passages in our AI humanizer without switching tools.

Pros

• No sign-up needed for guest checks
• Per-sentence highlighting plus a plain-language explanation of the signals behind the score
• Burstiness and vocabulary stats help you see why text reads as AI-like
• Built-in humanizer for reworking flagged passages in your own writing

Cons

• A newer tool that hasn’t been part of the independent studies cited in this post
• Lower per-check limits (600 or 1,000 words) than GPTZero or ZeroGPT
• No plagiarism checker, LMS integration or API yet
• Scores come from an AI model, so they can shift with edits and text length, as with every detector

Pricing: The AI detector is free as of November 2026. Humanizer plans start at $7.99/month, or $4.99/month billed yearly. See our pricing page.

Try it: HumanizeGo AI detector

2. GPTZero — best free AI detector for teachers

GPTZero is one of the best-known AI detectors in education. Its free scan box accepts up to 10,000 characters per scan without an account, and GPTZero asks you to create a free account for longer scans. Third-party trackers report a free monthly word allowance for account holders, but check their site for the current figure. Results use color-coded sentence highlighting, and you can upload files or use the Chrome extension and Google Docs add-on.

GPTZero claims “99.9% accuracy.” More usefully, an independent 2025 Chicago Booth working paper (Jabarian & Imas) found GPTZero kept false positives below 1% on long human passages and missed very little AI text.

Pros

• Generous free per-scan limit without an account
• Clear sentence-level highlighting
• Strong result in an independent 2025 study
• Chrome extension and Google Docs add-on

Cons

• Writing Replay (watching a document being written) needs the Premium plan
• Paid prices didn’t display on its pricing page during our check
• Full language support covers five languages: English, German, Portuguese, French and Spanish

Pricing: Premium and Professional plans, with GPTZero advertising up to 45% off for annual billing. Check gptzero.me/pricing for current prices (November 2026).

Official site: gptzero.me

3. ZeroGPT — best for long passages without an account

ZeroGPT has one of the biggest free limits: 15,000 characters per check, which ZeroGPT describes as “$0 forever” with no credit card needed. You get a percentage gauge plus sentence highlighting, and you can upload files, including in batches. The same site also offers a humanizer, paraphraser, translator and plagiarism checker.

ZeroGPT claims 98.4% detection accuracy and a false positive rate under 1%. Those are its own figures, and ZeroGPT wasn’t one of the tools in the independent studies we cite.

Pros

• Large free limit per check with no account
• Sentence highlighting and a clear overall gauge
• File and batch upload
• Pay-as-you-go API for developers

Cons

• Accuracy claims aren’t backed by the independent research we reviewed
• Paid prices didn’t display on its pricing page during our check
• The busy multi-tool site can be confusing if you only want detection

Pricing: Paid Pro plan, with ZeroGPT advertising 40% off for annual billing. Check zerogpt.com/pricing for current prices (November 2026).

Official site: zerogpt.com

4. QuillBot AI Detector — best for QuillBot users

QuillBot’s AI detector sits inside the same suite as its paraphraser, grammar checker and humanizer. QuillBot’s help pages describe free scans with no sign-up for shorter texts and a daily scan cap. We couldn’t load the official pages to confirm the exact limits, so check their site. Results highlight sentences and include an explanation (one per scan on the free plan).

Pros

• No sign-up for short free checks
• Sentence highlighting with explanations
• Handy if you already use QuillBot for writing

Cons

• Daily scan cap on the free plan
• Only one explanation per scan on the free plan
• Language support is described inconsistently across QuillBot’s pages

Pricing: Higher limits come with QuillBot Premium. Check quillbot.com for the current price (November 2026).

Official site: QuillBot AI Detector

5. Grammarly AI Detector — best for Grammarly users

Grammarly offers a free AI detector with a percentage score, flagged phrases with explanations and document upload. It doesn’t state a word cap, and sign-up is encouraged but not stated as required. Grammarly Pro adds an “AI Detector agent” with phrase-level identification and citation support.

Grammarly claims 99% detection accuracy and says it ranks #1 on the RAID benchmark. It also states that “No AI detector is 100% accurate,” which is a fair caveat.

Pros

• Free scan and file upload
• Flagged phrases come with explanations
• One-click rewrites through Grammarly’s AI Rewriter
• Fits into the Grammarly editor many people already use

Cons

• Grammarly says its model was trained on AI text created before 2021
• Supported languages aren’t specified
• USD pricing for Pro couldn’t be confirmed on the official plans page

Pricing: Advanced features come with Grammarly Pro. Check grammarly.com/plans for current prices in your region (November 2026).

Official site: Grammarly AI Detector

6. Pangram — best for avoiding false positives

Pangram is built around one goal: not flagging human writing. It claims a false positive rate of “1 in 10,000,” and the 2025 Chicago Booth paper found Pangram’s false positives were near zero, the lowest of the tools tested. The free option needs sign-up. Pangram’s homepage mentions twenty free checks a day on a free plan, while its pricing page shows a 7-day trial, so check their site for current terms.

Pros

• Lowest false positives in an independent 2025 study
• Similarity (plagiarism) detection on every scan
• Browser extension, Google Docs and Gmail support, file upload with OCR
• API priced at $0.05 per 100 words

Cons

• Free use requires an account
• Free plan details conflict between Pangram’s own pages
• Paid plans cost more than most tools here

Pricing: Individual is $20/month for 300,000 words; Pangram says annual billing saves $60. Professional is $65/month (November 2026).

Official site: pangram.com

7. Originality.ai — best for publishers and SEO teams

Originality.ai is aimed at content teams. Its AI checker lets you run a free scan without an account, capped at 100 credits per account (one credit covers 100 words), with a 100-word minimum. Its pricing page describes the free tier differently, so check before relying on it. Paid plans add plagiarism, fact-checking, readability and bulk scans.

In the 2025 Chicago Booth paper, Originality.ai kept false positives below 1% but missed more AI text than GPTZero or Pangram (roughly 10% to 40%, depending on the test).

Pros

• Combines AI, plagiarism, fact-check and readability checks
• Sentence-level highlighting and shareable reports
• Browser extension with writing replay

Cons

• Very small free allowance
• Text entered in the free tool may be used for training unless you have an account and opt out
• API access only on the Enterprise plan ($179/month)

Pricing: Pro is $14.95/month, or $12.95/month billed annually, for 200,000 words a month (November 2026).

Official site: originality.ai

8. Sapling AI Detector — best for developers

Sapling’s detector scores the first 2,000 characters of each check for free and highlights each sentence. You can paste text, upload PDF or Word files, or enter a URL. Registering gets you a one-time free month of Pro. Sapling is unusually candid, stating on its site that “False positives and false negatives will occur.”

Pros

• Per-sentence scoring and highlighting
• Metered API with a $5 minimum, useful for developers
• Chrome extension and batch file checks

Cons

• Free checks stop at 2,000 characters (about 300 to 350 words)
• Shareable report links expire after 3 days
• Auto-detection covers 16 languages; others are scored with the English model, which Sapling calls less reliable

Pricing: Pro is $25/month, or $12/month billed annually, with 100,000 characters per check (November 2026).

Official site: Sapling AI Detector

9. Scribbr AI Detector — best for one-off thesis checks

Scribbr is best known for proofreading and plagiarism checks for students. Its AI detector has a free version, and third-party reviews describe free checks with no sign-up and a per-check word limit. We couldn’t confirm the limits on Scribbr’s own site, so check their site. A premium AI check is bundled with Scribbr’s paid plagiarism check rather than sold as a subscription.

Pros

• Free checks aimed at students
• Premium AI check comes with a plagiarism check in one order
• No subscription needed

Cons

• Reviews report the free version targets older GPT models
• Pay-per-document pricing gets expensive for frequent checks
• Current free limits couldn’t be verified on the official site

Pricing: Premium AI detection is included with a paid plagiarism check, priced per document. Check scribbr.com for current prices (November 2026).

Official site: Scribbr AI Detector

10. Copyleaks AI Detector — best for AI and plagiarism checks together

Copyleaks combines AI detection with a plagiarism checker that covers 100+ languages, plus a Chrome/Edge extension, an API and AI image detection. Its free use is limited, and we couldn’t confirm exact free limits or prices because its official pages blocked our checks. Copyleaks claims 99% accuracy on internal English datasets and a 0.2% false positive rate, and its own help center says accuracy is lower on short text and creative writing.

Pros

• AI and plagiarism detection from one vendor
• Browser extension, API and LMS integrations
• AI detection in 30+ languages, per Copyleaks

Cons

• Credit-based pricing that third-party sources describe inconsistently
• Lower accuracy on short and creative text, by Copyleaks’ own account
• Small free allowance

Pricing: Paid plans use credits. Check copyleaks.com/pricing for current prices (November 2026). We compare other options in our list of Copyleaks alternatives.

Official site: Copyleaks AI Detector

Which other AI detectors did we leave out, and why?

A few tools people search for didn’t make the list:

• Winston AI offers a 14-day trial with 2,000 credits and no credit card, not a permanent free plan. It’s a strong option for teachers who need OCR on scanned or handwritten work; see our best AI detectors for essays.
• Netus AI includes an unlimited AI detector on its free plan (sign-up required), but it’s mainly a rewriting tool.
• Turnitin has no free version. Only institutions can license it.
• Writer.com AI Content Detector has been discontinued. If you search for the “Writer AI content detector,” the old page now loads Writer’s enterprise homepage.
• BrandWell (formerly Content at Scale) AI detector is effectively gone. The old “Content at Scale AI detector” URL now redirects to an unrelated third-party tool.
• OpenAI’s GPT-2 Output Detector is a legacy model that its own model card says shouldn’t be used to detect ChatGPT. We cover it in GPT-2 Output Detector and GLTR.

If you mainly want to catch ChatGPT text, see our separate list of the best ChatGPT detectors.

How accurate are free AI detectors?

Accuracy varies widely between AI detectors, and free versus paid matters less than which model a tool uses. A few findings worth knowing:

• Even OpenAI struggled. OpenAI withdrew its own AI Text Classifier on 20 July 2023, citing low accuracy. At launch it correctly identified only 26% of AI-written text (Search Engine Land).
• Non-native writers get flagged more. A 2023 Stanford study found seven detectors misclassified 61.22% of TOEFL essays by non-native English writers as AI-generated on average (Liang et al.).
• The best tools have improved. The 2025 Chicago Booth paper found GPTZero, Originality.ai and Pangram kept false positives below 1% on longer human passages, while an open-source model performed close to random.
• Short text is hard for everyone. In the same study, all detectors got worse on passages under 50 words.

We go through this evidence in detail in Are AI detectors accurate?

How we chose

We reviewed each tool’s official pricing pages, feature pages and documentation in November 2026, and used the facts on those pages to compare free limits, sign-up rules and paid prices. Where an official page blocked access or didn’t display prices, we say “check site” rather than guess. Accuracy figures quoted here are either labeled as the vendor’s own claims or come from published independent research we link to. We did not run our own accuracy tests or benchmarks for this article.

We ranked tools by how useful the free tier is for a typical person: how much you can check without paying, whether you need an account, and how clearly the results explain themselves. We excluded tools that have been discontinued.

How to choose a free AI detector

Start with what you’re checking and why:

1. Checking your own draft? Pick a tool with sentence highlighting and explanations, like HumanizeGo, QuillBot or Grammarly, so you can see which passages to revise.
2. Checking student work? Use a detector built for education, like GPTZero, and pair it with drafts and a conversation. Our guide on how to check if text is AI generated walks through a fair process.
3. Checking long documents? ZeroGPT and GPTZero have the largest free per-check limits without an account.
4. Worried about false accusations? Favor tools with low false positives in independent research, like Pangram or GPTZero.
5. Need plagiarism checks too? Copyleaks, Originality.ai and Pangram combine both. HumanizeGo doesn’t check plagiarism.
6. Building something? Sapling and Pangram have clearly priced APIs.

Whatever you choose, run important text through at least two different detectors, and never treat one result as the only evidence against a person.

The bottom line

The best AI detectors with free tiers in 2026 are good at flagging long, unedited AI text and weaker on short, edited or non-native writing. Pick a tool that shows its reasoning at the sentence level, and treat every score as a starting point.

To try one now, paste a passage into the HumanizeGo AI detector. It’s free with no sign-up, highlights each sentence and explains its score. If your own writing reads stiff, our AI humanizer can help you revise it, though no tool can guarantee a particular detector result. For humanizer comparisons, see the best AI humanizers.