The best AI detectors in 2026, and what they catch and miss

How an AI detector works

An AI detector estimates how likely it is that a chatbot wrote a piece of text. It looks for patterns that AI writing tends to share, such as predictable word choices and sentences of similar length and shape. The result is a percentage, often with the suspect sentences highlighted.

That percentage is a likelihood, not proof, because a detector can't see how the text was written. A plain, formulaic essay can look like AI, and edited AI text can look human. Most tools also need a minimum length: QuillBot asks for 80 words, Originality.ai for 100 and Turnitin for 300.

A plagiarism checker does a different job: it compares your text with web pages, papers and books to find copied passages. Every tool here does both, some only on paid plans.

Detectors are trained on text from chatbots such as ChatGPT, Claude and Gemini, and we explain how those three compare. Students who want study help rather than checks can start with our guide to the best AI tools for students.

The best AI detectors at a glance

Prices are per person per month, billed monthly, from each maker's own pages on Nov 8, 2026. Languages are the ones each maker says its AI check reads.

Tool	Free use	Paid from	Plagiarism check	AI check languages	Best for
Originality	100 credits once (10,000 words)	$14.95	Yes	31	Editors and publishers
Turnitin	No	Schools only	Yes	7	Schools that license it
QuillBot	1,200 words a scan, 6 a day	$19.95	Yes	20+	Free checks
GPTZero	10,000 words a month	$23.99	Yes	English plus 20+	Teachers buying their own
Copyleaks	25,000 characters a scan, no account	$16.99	Yes	30+	Many languages
Winston AI	2,000 words for 14 days	$18	From $29	9	Scanned and handwritten work
Grammarly	A score for each scan	$30	On Pro	Not listed	Students checking their own work
Quetext	1,000 words	$7.99	Yes	17 or 25 (pages differ)	AI and plagiarism on a budget

The eight best, one by one

2. Turnitin: best for schools

• TurnitinBest for schoolsPaid

Turnitin is the detector many schools and universities already pay for. Its AI writing report sits beside the similarity report in your school's learning platform. In English, it also flags AI text that went through a paraphraser or a humanizer.

You can't buy it yourself: AI detection comes only with a school's Turnitin Originality license, and prices aren't public. A file needs 300 to 30,000 words of prose. Scores from 1% to 19% show only as an asterisk, because Turnitin says low scores produce more false positives.

Good

• Built into the tools schools already use
• Hides low scores, where false flags are more common
• Spots paraphrased and humanized AI text in English

Watch for

• Schools only, with no public price
• Skips bullet points, tables, poems and code

3. QuillBot: best free AI detector

• QuillBotBest freeFree

QuillBot offers free scans of up to 1,200 words each, six times a day, with no paid plan needed. Each scan gives a 0 to 100% score with sentence highlights, and it separates AI-written text from human writing polished with AI.

Premium costs $19.95 a month, or $99.95 a year, and removes the limits and adds downloadable reports. QuillBot says its detector reads more than 20 languages and leans toward "human" when a result is unclear, to cut false flags.

Good

• 1,200 words a scan, six scans a day, free
• Separates fully AI text from AI-polished human text
• Leans toward "human" when unsure

Watch for

• Also sells a humanizer that rewrites AI text
• Texts under 80 words can't be scanned

4. GPTZero: best for teachers buying their own

• GPTZeroBest for teachersFree

GPTZero is built mainly for teachers, and the American Federation of Teachers names it its official AI detector partner. It marks sentences that look AI-written and flags text run through paraphrasers and bypass tools. In Google Docs, it can replay a document being written.

The free plan checks 10,000 words a month, while Premium, at $23.99 a month, covers 300,000 words and adds more than 20 languages. Professional costs $45.99 a month, with uploads of up to 250 files and links to Canvas and Google Classroom. GPTZero says it is 99.9% accurate.

Good

• 10,000 free words a month
• Writing replay inside Google Docs
• Class uploads and LMS links on Professional

Watch for

• Other languages need a paid plan
• Free scans stop at 10,000 characters each

5. Copyleaks: best for many languages

• CopyleaksBest for many languagesFreemium

Copyleaks checks AI writing in more than 30 languages and plagiarism in more than 100, in one report. You can scan up to 25,000 characters free without an account. It can also read photos of handwritten work and check images for AI.

Personal costs $16.99 a month for 100 credits, and one credit covers 250 words, so about 25,000 words. Pro costs $99.99 a month for 1,000 credits and 25 users. Schools pay per student and get links to Canvas, Moodle and Blackboard. Copyleaks says it is over 99% accurate, with a 0.03% false-positive rate.

Good

• Free scans up to 25,000 characters, no account
• AI checks in 30+ languages, plagiarism in 100+
• Reads handwritten work from photos

Watch for

• Personal covers only about 25,000 words a month
• Switching plans wipes unused credits

Are AI detectors accurate?

AI detectors are often right about long AI text that nobody edited, but none is accurate enough to prove anything on its own. Every accuracy figure in this guide comes from the maker, and most claim 99% or more. Turnitin says it aims to wrongly flag fewer than 1 in 100 fully human documents.

Independent research is less kind: in a 2023 Stanford study published in the journal Patterns, seven detectors were near perfect on essays by U.S. eighth-graders. But they labeled 61% of essays by non-native English writers as AI, and at least one detector flagged 97% of those essays.

A peer-reviewed 2023 test of 14 tools, including Turnitin, called them "neither accurate nor reliable", and paraphrasing made the results worse. A 2024 study of six detectors saw accuracy fall from 39.5% to 17.4% after simple tricks, such as adding spelling errors.

Newer paid tools seem to do better. In a 2025 Chicago Booth working paper, three paid detectors, including GPTZero and Originality.ai, wrongly flagged about 2% or less of human writing. All three lost some accuracy on passages under 50 words, though GPTZero stayed at 96%.

The makers share these warnings, and OpenAI, which makes ChatGPT, says detectors have not worked in its experience. Its own test detector labeled Shakespeare and the Declaration of Independence as AI writing. Turnitin, Originality.ai and QuillBot all say a score should never be the only basis for a decision.

Small error rates add up across a school, which is one reason Vanderbilt University turned off Turnitin's AI detector in 2023. It noted that a 1% false-positive rate on the 75,000 papers it submitted in 2022 could have wrongly flagged about 750 of them.

Do AI detectors work in other languages?

Some do, but coverage varies a lot, so check that your language is listed before you trust a score.

• Copyleaks reads more than 30 languages, and Originality.ai reads 31.
• GPTZero reads English plus more than 20 others on its paid plans, and QuillBot says it covers more than 20.
• Winston AI reads nine, including simplified Chinese, Polish and Ukrainian.
• Turnitin reads seven: English, Spanish, Japanese, Arabic, Dutch, German and Turkish. Its paraphrase and humanizer checks work in English only.
• Quetext lists 17 languages on one page and 25 on another, and Grammarly doesn't list any.

Translation is a weak spot: in the 2023 test of 14 tools, human essays machine-translated into English were classed correctly about 20% less often. The authors warn that students who translate their own work risk false accusations.

What to do if a detector flags your writing

If a detector flags work you wrote yourself, gather your evidence before you reply, since even the makers call a score an estimate.

• Show your process. Version history in Google Docs or Word shows the document growing over time. Grammarly Authorship and Originality.ai's writing replay record the typing itself.
• Ask for the report. Students don't see Turnitin's AI report unless a teacher shares it.
• Quote the maker. Turnitin says its score shouldn't be the only basis for action against a student.

Teachers should treat a high score as a reason to talk, not as a verdict. Vanderbilt suggests comparing the work with the student's earlier writing and checking for made-up sources. Where AI use is allowed, OpenAI suggests asking students to share their chatbot conversations.

Which one should you pick?

• You check freelance writing and want AI and plagiarism in one scanOriginality
• Your school already licenses Turnitin and you grade in its learning platformTurnitin
• You want a free checker for the occasional essayQuillBot
• You teach and want class uploads and writing replayGPTZero
• You check writing in many languagesCopyleaks
• You need to check handwritten or scanned workWinston AI
• You're a student who wants to check a draft and show how you wrote itGrammarly
• You want AI and plagiarism checks for a class on a small budgetQuetext

How we picked

We started from the AI text detectors on Recaply and kept those that teachers, editors and students can get, alone or through a school. We read each maker's pricing pages, help centres and accuracy notes on Nov 8, 2026.

We have not run our own detection tests, so accuracy numbers are the makers' own claims unless we name an outside study. We left out tools whose main product rewrites AI text to slip past detectors.

No maker paid to appear in this list or saw it before publication. If a price changes, we update this page and its date.

Questions people ask