The best AI content detectors, tested and ranked

Turnitin came first of five with 4 out of 5, the only detector to score above 2.5. It got 88 of our 100 texts right, wrongly flagged 4 of the 40 human texts (10%) and missed 8 of the 60 AI or edited texts (13.3%). At 14.1 seconds per text, it was the fastest too. Its best parts were false-positive rate and speed, at 4.5 each. Our full Turnitin review has the details.

Turnitin is a similarity checker used by schools and universities, with an AI writing indicator added in 2023. It matches work against web content, licensed databases and a student-paper archive, and an AI report estimates how much looks AI-written. Since September 2025 it can also flag text changed by humanizer tools in English, and its Clarity add-on gives students a drafting space that records revision history.

The catch is access and trust. You can't buy it as an individual, there is no public price, and its rating on Trustpilot is 1.3 out of 5 from 78 reviews (checked November 2026), mostly over false flags, while institutional users rate it 4.2 out of 5 on G2 from 220 reviews. Curtin University switched off its AI detection from January 1, 2026, and ACU dropped it in March 2025. Turnitin itself says its AI score should not be the only basis for action against a student.

Winston AI came second with 3.5 out of 5, its best mark being 4.5 for ease of use. It got 77 of our 100 texts right, wrongly flagged 8 of the 40 human texts (20%) and missed 15 of the 60 AI or edited texts (25%). It took 24.7 seconds per text. That's the best result of the tools anyone can buy, but it still means one in five human texts was called AI. Read our Winston AI review for more.

Winston AI gives each text a human-versus-AI score from 0 to 100 and a sentence-by-sentence map of what looks AI-written. Every plan also includes plagiarism checks, AI image detection, OCR for scanned or handwritten pages and shareable PDF reports. It connects with Chrome, Google Classroom, WordPress and Zapier, and lists SOC 2 Type 2 and GDPR on its help centre.

It has the cheapest yearly entry here, at $5 a month, billed yearly, or $18 for one month billed monthly. The free plan is really a 14-day trial with 2,000 credits and no card needed. Be careful with yearly plans: they can't be cancelled during the term, and prorated refunds are usually not offered. On Trustpilot it has 4.3 out of 5, but from only 24 reviews (checked November 2026).

GPTZero came third with 2 out of 5. It got 73 of our 100 texts right, wrongly flagged 9 of the 40 human texts (22.5%) and missed 18 of the 60 AI or edited texts (30%). It was the slowest detector we tested, at 30.2 seconds per text. Accuracy and ease of use were its best parts, at 2.5 each. Our GPTZero review covers the full test.

GPTZero started as a student project and is now used heavily by teachers. It scores text for the likelihood it was written by models such as ChatGPT, Claude and Gemini and highlights the sentences it flags. It works in the browser, as a Chrome extension and in Google Docs, connects with Canvas and Google Classroom, and adds Writing Replay, which shows how a document was typed over time.

Its free plan is the most generous here, at 10,000 words a month with a basic scan and one advanced scan. Paid plans are shown only billed yearly, from $8.33 a month. Users are unhappy, though: it has 2.1 out of 5 on Trustpilot from 146 reviews (checked November 2026), mostly about charges on trials and slow cancellations. In June 2026, Superhuman agreed to buy GPTZero.

Originality.ai came fourth with 2 out of 5. It got exactly the same counts as GPTZero: 73 of our 100 texts right, 9 of the 40 human texts wrongly flagged and 18 of the 60 AI or edited texts missed. It was faster, at 24.3 seconds per text, and scored 2.5 for false-positive rate and speed, but only 2 for accuracy, ease of use and value. More in our Originality.ai review.

Originality.ai launched in November 2022 for people who buy written content, and it still aims at agencies, publishers and SEO teams. One scan gives an AI probability with sentence highlights and a plagiarism result, and you can also run fact and hallucination, readability, grammar and guideline checks. Account holders can opt out of their text being used for training.

Users rate it the highest of the five, at 4.5 out of 5 on Trustpilot from 1,366 reviews (checked November 2026), with praise for helpful support. Complaints are about human text flagged as AI and scores changing between scans. Pro is $14.95 for one month, billed monthly, and you can cancel any time, but the refund policy doesn't cover subscriptions.

Copyleaks came last of five with 1.5 out of 5, with its lowest marks for accuracy and false positives. It got 71 of our 100 texts right, wrongly flagged 10 of the 40 human texts (25%) and missed 19 of the 60 AI or edited texts (31.7%), the most mistakes of both kinds in our test. It took 27.5 seconds per text. Our Copyleaks review has the full results.

Copyleaks began as a plagiarism checker in 2015 and has added AI text, image and video detection. It covers AI detection in more than 30 languages and plagiarism in more than 100, the widest range here. It connects with Canvas, Moodle, D2L Brightspace, Schoology, Sakai, Edsby and Blackboard, and offers an API, a WordPress plugin and on-premises or private cloud hosting for enterprises.

It lists PCI DSS, SOC 2, SOC 3 and GDPR on its homepage. Users are lukewarm, at 2.6 out of 5 on Trustpilot from 386 reviews (checked November 2026), with doubts about detection accuracy that match what we saw. The Personal plan is $13.99 a month, billed yearly, and there are free AI detector and plagiarism tools for individuals.