The short answer
The Copyleaks AI detector is fairly accurate, but less accurate than its marketing says. In Plagino's March 2026 test of 1,000 documents, Copyleaks caught 91.3% of AI-written documents and wrongly flagged 2.2% of human-written ones. Copyleaks' own September 2026 test reports a 0.30% false positive rate. Plagino caught 97.4%; Turnitin caught 98.2%.
What is the Copyleaks AI detector?
The Copyleaks AI detector is a classifier that estimates whether text was written by a person or produced by a large language model such as ChatGPT, Claude or Gemini. It is one part of a wider suite from Copyleaks, a company founded in 2015 by Alon Yamin and Yehonatan Bitton, which started as a plagiarism checker and later added AI detection.
What a Copyleaks AI scan returns
A text scan gives an overall verdict plus sentence-level highlights, and Copyleaks' "AI Logic" feature shows which phrases pushed the score toward AI. Text scans also run a plagiarism check in the same report. Copyleaks says its AI detection works in 30+ languages, and its testing page lists results for Claude, Gemini, Grok and OpenAI model families.
Where you can use it
You can paste text or upload a file in the web app, scan pages with the Chrome extension, use the Google Docs add-on, call the API, or run it inside a learning management system. Copyleaks lists integrations with Canvas, Moodle, D2L Brightspace, Schoology, Sakai, Edsby and Blackboard. That reach is why many students meet Copyleaks through a school, not by choice.
How accurate is the Copyleaks AI detector in independent testing?
On documents it had never seen, Copyleaks caught about 9 in 10 AI-written documents and wrongly flagged about 1 in 45 human-written ones. We ran it through the same test as every other tool in Plagino's benchmark: 1,000 documents, 500 written by AI (GPT-4o, Claude and Gemini, some lightly edited by a person) and 500 written by people. Each tool saw the same files through its own web app on default settings in March 2026. A document counted as flagged if the tool flagged it at all.
What the detection rate tells you
Copyleaks missed more AI writing than Plagino, Turnitin or Originality.ai. A 91.3% detection rate means roughly 1 in 11 AI-written documents passed unflagged. Its interval (88.5–93.5%) does not overlap Plagino's (95.6–98.5%) or Turnitin's (96.6–99.1%), so the gap is larger than sampling noise.
What the false-positive rate tells you
The false-positive rate is the number a student should care about most, because it is the one that leads to an unfair accusation. Copyleaks wrongly flagged 2.2% of human documents, against 0.8% for Plagino and 1.4% for Turnitin. Here the intervals overlap, so on 500 human documents we cannot say Copyleaks is definitely worse than either. It did flag far fewer human documents than GPTZero (5.7%) and Originality.ai (4.1%).
| Detector | AI documents caught | 95% interval | Human documents wrongly flagged | 95% interval |
|---|---|---|---|---|
| Turnitin (reference) | 98.2% | 96.6–99.1% | 1.4% | 0.7–2.9% |
| Plagino | 97.4% | 95.6–98.5% | 0.8% | 0.3–2.0% |
| Originality.ai | 95.6% | 93.4–97.1% | 4.1% | 2.7–6.2% |
| Copyleaks | 91.3% | 88.5–93.5% | 2.2% | 1.2–3.9% |
| GPTZero | 88.9% | 85.8–91.4% | 5.7% | 4.0–8.1% |
How do Copyleaks' own accuracy numbers compare?
Copyleaks reports much better numbers than any outside test, and it publishes three different figures depending on where you look. Its AI detector page advertises "over 99% accuracy" and "an industry-low .03% false positive rate". Its testing methodology page for the V11 model, tested on 10 September 2026 and published 28 September 2026, reports a 0.30% false positive rate at the default setting. Ours measured 2.2%.
What Copyleaks actually tested
Copyleaks' QA team tested 326,120 human-written texts and 128,225 AI-generated texts, all in English and all longer than 350 characters, which is the minimum the product accepts. It wrongly called 923 human texts AI-written. Student essays were its easiest category: 6 errors in 74,212 essays (99.99%). Articles, news, blogs and social posts were the hardest, at 99.29%. A separate data science team test on 500,000 "extra-hard" texts, including adversarial attacks, reported 98.9% of AI texts and 99.9% of human texts classified correctly.
Why our numbers are lower
Vendor tests and independent tests answer different questions. Copyleaks built its own test sets and ran them through its API. An outside test uses documents the vendor has never seen, through the web app a normal user sees, and scores at document level, so one flagged sentence in a human essay counts as a false positive. Results almost always drop. A 2023 study in the International Journal for Educational Integrity tested 14 detection tools and concluded they were "neither accurate nor reliable".
Timing matters too. Our run was in March 2026, and Copyleaks' V11 results are from September 2026, so a newer model may do better than the one we tested. Read 91.3% and 2.2% as what Copyleaks did on our corpus in March, not a permanent rating.
| Source | Date | Human text wrongly flagged | AI text missed |
|---|---|---|---|
| Copyleaks AI detector page (headline) | checked Oct 2026 | 0.03% | not stated |
| Copyleaks V11 methodology, "Balanced" default | tested 10 Sep 2026 | 0.30% | 0.64% |
| Copyleaks V11, "Extra Safe" | tested 10 Sep 2026 | 0.16% | 0.88% |
| Copyleaks V11, "Extra Sensitive" | tested 10 Sep 2026 | 0.66% | 0.49% |
| Plagino benchmark (Copyleaks web app, default) | Mar 2026 | 2.2% | 8.7% |
What do Copyleaks' sensitivity levels change?
Copyleaks lets you trade missed AI text against false accusations with three sensitivity levels, available since model v7.1. "Extra Safe" adds filters to cut false positives (0.16%) but misses more AI text (0.88%). "Balanced", the default, sits in the middle. "Extra Sensitive" targets text run through a humanizer or text spinner and accepts more false positives (0.66%).
The practical point: if your school's report came from Copyleaks, ask which sensitivity level was used. The same essay can pass on "Extra Safe" and be flagged on "Extra Sensitive". Copyleaks' figures show that moving from Extra Safe to Extra Sensitive roughly quadruples its own false positive rate.
Does Copyleaks detect ChatGPT, Claude and Gemini?
Yes, on unedited output Copyleaks detects all three major model families well, by its own testing. Its V11 results list 99.15% accuracy on OpenAI-family texts, 99.83% on Claude, 99.00% on Gemini and 98.72% on Grok. Our benchmark's AI set was also built from GPT-4o, Claude and Gemini, and that is where Copyleaks' 91.3% comes from, including some lightly human-edited documents.
Edited and paraphrased AI text
Detection falls once a person or a paraphrasing tool rewrites the text. A University of Adelaide analysis reported by Wikipedia found Copyleaks gave an original AI text an 85.2% AI probability, falling to 73.1% after human alteration. That is still a flag, but a weaker one, and heavily edited drafts sit exactly where every detector is least reliable.
What does Copyleaks cost, and is the AI detector free?
Copyleaks has a limited free option and paid plans priced in credits, where one credit covers up to 250 words. The figures below come from the Copyleaks pricing page as checked in October 2026. Prices and allowances change often, so confirm on copyleaks.com/pricing before you buy.
Credits versus scans
The two pricing models suit different habits. Copyleaks charges by length, so a 5,000-word chapter uses about 20 credits per scan. Plagino charges by scan, so re-checking the same long chapter after each edit costs one scan each time. A student revising one dissertation many times usually gets further on a scan allowance; a team scanning many short web pages usually gets further on credits.
| Copyleaks | Plagino | |
|---|---|---|
| Free use | Limited free scans; a free account adds a small monthly credit allowance | 3 scans a month, no card |
| Entry paid plan | Personal: $16.99/month, or $13.99/month billed annually | Pro: $19/month |
| Usage on that plan | 100 credits a month (about 25,000 words) on monthly billing | 20 scans a day |
| Higher plan | Pro: $99.99/month, or $74.99/month billed annually | None |
| Schools and teams | Education and Enterprise: custom pricing | Team: custom pricing |
| What you submit | Paste, file upload, browser extension, Google Docs add-on, API, LMS | .docx upload in the web app |
| Report | AI score with AI Logic, plus plagiarism results | PDF with sentence-level AI highlights and matched sources |
What happens to the document you upload to Copyleaks?
Read the Copyleaks privacy policy before you upload coursework. The policy lists "to train our models" among the uses of submitted content and says you can opt out by contacting support. It also describes a Shared Data Hub: when enabled, your scans join a database that other users' submissions are compared against. The policy says you can disable it and permanently delete files from it.
If you are pre-checking a draft you will later submit through your school, decide whether you want it stored in that database first. A copy of your own draft in a shared index is one way a paper can later match itself.
Copyleaks vs Plagino: which should you use?
Pick Copyleaks if you need web plagiarism coverage, non-English text or an LMS integration; pick Plagino if you are a student pre-checking an English academic draft and care most about avoiding a false flag. Plagino is our tool, so weigh this section accordingly.
Where Plagino's AI detector fits
Plagino's AI detector reports which sentences look AI-written in a .docx draft, with a PDF you can keep, and pairs it with a plagiarism check against open-access academic literature. It cannot see Turnitin's or Copyleaks' private repositories of student papers, and neither tool can see the other's. For the full field of detectors, see our list of the best AI detectors.
| If you need… | Better fit | Why |
|---|---|---|
| Plagiarism matching against the open web | Copyleaks | It searches web pages; Plagino matches against open-access research via CORE only |
| AI detection in languages other than English | Copyleaks | 30+ languages for AI detection; Plagino is built for English academic drafts |
| AI and plagiarism checks inside Canvas or Moodle | Copyleaks | Seven LMS integrations; Plagino has none |
| Images, source code or browser scanning | Copyleaks | Plagino accepts .docx files only |
| Fewest missed AI documents in our test | Plagino | 97.4% caught vs 91.3% |
| Fewest false flags on human writing in our test | Plagino | 0.8% vs 2.2% (intervals overlap) |
| Re-checking one long draft many times | Plagino | 20 scans a day on Pro instead of word-based credits |
| A sentence-level report to show a tutor | Either | Both highlight the sentences behind the score |
How should you read a Copyleaks AI score?
Treat a Copyleaks AI score as a reason to look closer, never as proof. Every detector produces false positives, and they fall unevenly. A 2023 Stanford study found several AI detectors misclassified more than half of TOEFL essays by non-native English writers as AI-generated. Copyleaks has not published a separate false positive rate for non-native English writing.
If a Copyleaks result has been used against you, ask for the full report, the sensitivity level and the scan date, and bring your drafts and version history. Our guide for students falsely accused of using AI walks through the process, and our explainer on AI detector false positives covers why borderline scores happen.
Test limits that apply to both tools
Our corpus was English only, so it says nothing about Copyleaks' multilingual detection, which is one of its strengths. The AI documents came from GPT-4o, Claude and Gemini; newer models may behave differently. With 500 documents per rate, the benchmark separates large gaps, like Copyleaks' detection rate, but not small ones, like the false-positive differences between Copyleaks, Plagino and Turnitin.
Frequently asked questions
Is the Copyleaks AI detector accurate?
It is reasonably accurate on unedited AI text, but less accurate than its marketing suggests. In Plagino's March 2026 benchmark of 1,000 documents, Copyleaks caught 91.3% of AI-written documents and wrongly flagged 2.2% of human-written ones. Copyleaks' own September 2026 test reports a 0.30% false positive rate at its default setting.
Can Copyleaks give false positives?
Yes. Every AI detector does, and Copyleaks' own testing reports false positives at all three sensitivity levels, from 0.16% to 0.66%. In our test it wrongly flagged 2.2% of human-written documents, so a flag should prompt a review of drafts, not be treated as proof.
Is the Copyleaks AI detector free?
Only in a limited way. Copyleaks offers a small free allowance, and paid plans start at $16.99 a month, or $13.99 a month billed annually, as of October 2026. Check copyleaks.com/pricing for current limits, which change often.
Is Copyleaks more accurate than Turnitin?
Not in Plagino's benchmark. Turnitin caught 98.2% of AI-written documents against 91.3% for Copyleaks, and wrongly flagged 1.4% of human documents against 2.2%. The false-positive gap is within the margin of error on 500 documents; the detection gap is not.
Is Copyleaks better than GPTZero?
On false positives, it was in our test. Copyleaks wrongly flagged 2.2% of human documents against GPTZero's 5.7%, and it caught slightly more AI documents, 91.3% against 88.9%. See Plagino vs GPTZero for the full comparison.
Can Copyleaks detect paraphrased or humanized AI text?
Less reliably than raw AI output. Copyleaks offers an "Extra Sensitive" setting aimed at text run through humanizers and spinners, but that setting has the highest false positive rate in its own tests. Independent work has found its AI probability drops when people edit AI text.
What is the minimum text length Copyleaks can check?
Copyleaks' testing page says the product accepts texts longer than 350 characters, roughly 60 words. Very short passages give a detector less to work with, so short answers are the least reliable to score.
What is the Copyleaks AI Logic feature?
AI Logic is Copyleaks' explanation layer: it highlights the phrases and patterns that pushed a passage toward an AI verdict. It helps you see why a sentence was flagged, but it does not make the underlying verdict more certain.
Does Copyleaks store my paper?
It can. Copyleaks' privacy policy says submitted content may be used to train its models unless you opt out through support. If the Shared Data Hub is enabled, your scans join a database that other users' submissions are compared against, and the policy says you can disable it and delete files.
Do universities use Copyleaks?
Some do. Copyleaks sells education plans and integrates with Canvas, Moodle, D2L Brightspace, Schoology, Sakai, Edsby and Blackboard. Our guide to what AI detector colleges use covers how to find out which tool your school licenses.
Which Copyleaks sensitivity level is the default?
"Balanced" is the default, and it is the setting behind Copyleaks' headline methodology results: 0.30% false positives and 0.64% false negatives on its V11 model. "Extra Safe" lowers false positives to 0.16% and "Extra Sensitive" raises detection of humanized text at 0.66% false positives.
Who owns Copyleaks?
Copyleaks is an independent company founded in 2015 by Alon Yamin, its CEO, and Yehonatan Bitton. It is not part of Turnitin, and Plagino is not affiliated with either company.
