Best AI Detectors in 2026: 8 Tools Compared on Features, Pricing and Published Accuracy

Updated October 16, 2026 – Tested Intelligence

The honest starting point: no AI detector is reliable enough to be the sole evidence in a decision that affects someone’s grade, job or contract. Every tool below can miss AI text and can flag human writing, so treat scores as a prompt for a human conversation, never as proof. That said, detectors differ a lot in features, workflow and price, and some are far better suited to classrooms, publishing desks or enterprise pipelines than others. This comparison uses each vendor’s published claims and independent published studies – it does not present our own test results.

Read this first: what the published evidence says about accuracy

Vendors quote impressive numbers – GPTZero, for example, states a 99% accuracy rate for classifying human text on its own site – but independent research paints a more cautious picture. A widely cited 2023 Stanford study (Liang and colleagues, published in Patterns) found that seven popular detectors misclassified more than half of TOEFL essays written by non-native English speakers as AI-generated, while almost never flagging essays by US students. A separate 2023 evaluation by Weber-Wulff and colleagues found the tools they examined were neither fully accurate nor reliable, and tended to lean toward calling text human. OpenAI itself retired its own AI Text Classifier in 2023, citing its low rate of accuracy. The practical takeaways: detectors are weakest exactly where the stakes are highest (formulaic, formal, or second-language writing), paraphrasing and editing degrade them further, and a second tool plus a human review is the minimum responsible workflow.

1. GPTZero

GPTZero is the best-known detector in education, built by a Princeton student in 2023 and now a full platform with sentence-level highlighting, a plagiarism checker, writing feedback and a “writing replay” feature that shows how a document was composed in supported editors. It states a 99% accuracy rate for human text on its own site; like all vendor numbers, treat that as a claim, not a measurement. Pricing: free plan with 10,000 words a month; Essential $14.99/month ($8.33 billed annually) for 150,000 words; Premium $23.99 ($12.99) for 300,000 words plus plagiarism checking; Professional $45.99 ($24.99) for 500,000 words, batch scanning and API access.

Best for: teachers and tutors who want a generous free tier and document-level detail.

2. Originality.ai

Originality.ai aims at publishers and content teams rather than classrooms. Alongside AI detection it bundles plagiarism checking, readability scoring, grammar and fact-checking in one scan, and its Pro plan can scan an entire website from a URL – useful for auditing a back catalogue. It runs on credits (1 credit covers 100 words of AI scanning): a free Basic tier allows 3 scans a day up to 2,000 words each; Pro is $14.95/month ($12.95 billed annually) with 2,000 credits a month; Enterprise is $179/month ($136.58 annually) with 15,000 credits and API access; pay-as-you-go credits start at $30 for 3,000 and last two years. Note that monthly subscription credits do not roll over.

Best for: blogs, agencies and content teams screening freelance submissions.

3. Copyleaks

Copyleaks is the enterprise-leaning pick: AI detection and plagiarism in a single report, detection across 30+ languages, AI-generated image detection, source-code checking, and a well-documented API, plus LMS integrations (Canvas, Moodle, Blackboard and others) for its education customers. It uses unified credits – one credit covers up to 250 words or one image. After a limited set of free scans, Personal costs $16.99/month ($13.99 billed annually) with 100 credits a month, and Pro costs $99.99/month ($74.99 annually) with 1,000 credits, team seats and website scanning. Education and Enterprise pricing is custom and not published.

Best for: organizations that need detection built into their own systems via API.

4. Turnitin

Turnitin is the detector most students will actually meet, because it is sold to institutions, not individuals – there is no way to buy a personal account, and Turnitin does not publish pricing. Its AI writing detection sits inside the same report as its long-established similarity (plagiarism) check, drawing on Turnitin’s huge database of student papers and publications, and it plugs into the LMS platforms schools already use. If your institution provides it, it is the reference point your work will be judged against; if it does not, you cannot get it, and the free tools in this list are your pre-check options.

Best for: universities and schools (institutional licenses only).

5. Sapling

Sapling’s detector is unusually generous for free use: the web tool checks text with sentence-level highlighting and no account required, though free checks are limited to 2,000 characters at a time. Sapling states its detector is updated as new models (including DeepSeek) appear, and it doubles as a writing assistant for customer-support and sales teams, with browser extensions and an API. Pro costs $25/user/month ($12 billed annually) and raises the per-check limit to 100,000 characters; Enterprise pricing is custom. The trade-off for the free access is depth – independent reviewers consistently place Sapling behind GPTZero and Originality.ai on difficult, edited text.

Best for: free, quick, sentence-level checks and support-team workflows.

6. ZeroGPT

ZeroGPT pairs a detector with a grab-bag of writing tools – paraphraser, summarizer, grammar checker, translator and its ZeroCHAT assistant. The vendor advertises accuracy of up to 98%; independent reviewers have found its real-world consistency more mixed, and its scores can swing between repeat scans of the same text. The free plan allows 15,000 characters per scan with ads. Paid tiers are cheap: Pro $9.99/month ($7.99 billed annually), Plus $19.99 ($14.99) and Max $26.99 ($18.99), adding PDF reports, batch scanning and larger limits.

Best for: casual users on a budget who want several writing tools in one subscription.

7. QuillBot AI Detector

QuillBot is primarily a paraphrasing and writing platform, and its AI detector is one tool in that suite. The free version checks up to 1,200 words per scan with limited access; full detector access comes with QuillBot Premium at $19.95/month, or $8.33/month billed annually ($99.95/year), which also unlocks unlimited paraphrasing, the plagiarism checker (25,000 words a month) and the rest of the suite. QuillBot itself cautions that its detector provides an estimate rather than certainty – an unusually honest disclaimer worth taking seriously for every tool on this page.

Best for: students and writers who already pay for QuillBot’s writing tools.

8. Scribbr

Scribbr’s AI detector is completely free, needs no account, and accepts up to 1,200 words per check – one of the least-friction ways to get a quick read on a passage. Scribbr’s money is made on its plagiarism checker, which is priced per document rather than by subscription: $19.95 for documents up to 7,500 words, $29.95 up to 50,000 words and $39.95 above that, using similarity technology comparable to what most universities run. A free detector score and a paid plagiarism report measure different things, so do not let confidence in one bleed into the other.

Best for: students who want a free pre-submission sanity check.

FAQ

Are AI detectors accurate enough to prove someone used AI?

No. Published independent studies show meaningful false-positive and false-negative rates, especially on formal writing and text by non-native English speakers. A detector score is a signal to look closer, not proof.

What is the best free AI detector?

For word volume, GPTZero’s free plan (10,000 words a month). For a no-account quick check, Scribbr or Sapling. Cross-checking a passage in two free tools is more informative than any single score.

Can AI detectors detect paraphrased or edited AI text?

Detection gets weaker as AI text is edited, paraphrased or mixed with human writing. Vendors work to close this gap – Originality.ai, for example, says it trains on paraphrased examples – but no tool reliably catches heavily edited AI text.

Bottom line

Teachers: start with GPTZero’s free tier, and use Turnitin if your institution provides it. Publishers: Originality.ai Pro is the best-matched workflow and price. Organizations building detection into a pipeline: Copyleaks. Everyone else: use the free tools – Sapling, Scribbr or GPTZero – and never let any single score make a high-stakes decision on its own.