The short answer
Fairly accurate, but less than Copyleaks advertises. 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 reports a 0.30% false positive rate in its own testing. Plagino caught 97.4% with 0.8% false flags; Turnitin caught 98.2%.
How accurate is the Copyleaks AI detector in independent testing?
We ran Copyleaks through the same test as every other detector in Plagino's benchmark. The corpus had 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. We counted a document as flagged if the tool flagged it at all.
Two numbers matter, and they measure different failures. The detection rate is the share of AI-written documents a tool caught. The false-positive rate is the share of human-written documents it wrongly called AI. A student cares most about the second number, because that is the one that leads to an unfair accusation.
| 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% |
| Copyleaks | 91.3% | 88.5–93.5% | 2.2% | 1.2–3.9% |
Copyleaks missed more AI writing than Plagino or Turnitin. Its 91.3% detection rate means roughly 1 in 11 AI-written documents went through unflagged, and its interval does not overlap with Plagino's or Turnitin's. That gap is large enough to be more than sampling noise.
On false positives the picture is closer. Copyleaks wrongly flagged 2.2% of human documents, against 0.8% for Plagino and 1.4% for Turnitin. The intervals overlap, so on 500 human documents we cannot say for certain that Copyleaks is worse than either. Turnitin, for its part, beat Plagino on detection by 0.8 points, also within the margin.
How do Copyleaks' own accuracy claims compare?
Copyleaks publishes more about its testing than most vendors. Its AI detector page claims "over 99% accuracy" and "an industry-low .03% false positive rate". Its own testing methodology page, for the V11 model tested on 10 September 2026, reports a 0.30% false positive rate and 0.64% false negative rate at the default "Balanced" setting. Those two figures differ by a factor of ten, so read the methodology page rather than the headline.
The methodology page is worth reading in full. Copyleaks tested 326,120 human-written texts and 128,225 AI-generated texts, all in English and all longer than 350 characters. It reports 99.99% accuracy on student essays and 99.29% on articles, news, blogs and social posts. The detector also has three sensitivity levels: "Extra Safe" (0.16% false positives), "Balanced" (0.30%) and "Extra Sensitive" (0.66%), the last aimed at text run through rewriting tools.
Why our numbers are lower than Copyleaks' numbers
Vendor tests and independent tests answer different questions. A vendor builds its own test sets, often from sources similar to its training data, and runs them through its API. An outside test uses documents the vendor has never seen, through the app a normal user would use. Results almost always drop. A 2023 study in the International Journal for Educational Integrity tested 14 detection tools and concluded that the available tools were "neither accurate nor reliable", with a bias towards calling AI text human.
Timing matters too. Our run was in March 2026; Copyleaks' V11 results are from September 2026. A newer model may do better than the one we tested, and we will re-run Copyleaks in the next quarterly benchmark. Until then, treat our 91.3% and 2.2% as what Copyleaks did on our corpus in March, not as a permanent rating.
What does Copyleaks cost and what does it check against?
Copyleaks is a combined AI and plagiarism checker. Text scans return AI detection and plagiarism matching in one report. The figures below come from the Copyleaks pricing page, its AI detector page and its plagiarism checker page, checked in October 2026. Prices change, so confirm on the vendor's site before you buy.
| Copyleaks | Plagino | |
|---|---|---|
| Free use | AI scans of up to 25,000 characters without logging in; a free account adds monthly credits | 3 scans per month, no card |
| Entry paid plan | Personal: $16.99/month, or $13.99/month billed annually ($167.88/year) | Pro: $19/month |
| Usage on that plan | 100 credits a month; 1 credit covers up to 250 words, so about 25,000 words | 20 scans per day |
| Higher plan | Pro: $99.99/month, or $74.99/month billed annually; 1,000 credits a month and 25 user seats | None |
| Schools and teams | Education and Enterprise: custom pricing; Education priced by full-time students | Team: custom pricing for departments and writing centres |
| Plagiarism check compares against | Web pages, 16,000+ open-access journals, code repositories and, if enabled, a Shared Data Hub of user submissions | Open-access academic literature via CORE only |
| AI detection | 30+ languages; AI image detection | Sentence-level highlights on a .docx upload |
| How you submit | Paste, file upload, browser extension, Google Docs add-on, LMS | .docx upload in the web app |
| LMS integrations | Canvas, Moodle, D2L Brightspace, Schoology, Sakai, Edsby, Blackboard | None |
| Report | AI score with AI Logic explanations and similarity report | PDF with sentence-level AI highlights and matched sources |
The source lists are the biggest practical difference. Copyleaks searches the open web, which Plagino does not. Plagino's plagiarism checker matches against open-access research through CORE, and each match points at the exact overlapping words. Neither tool can see Turnitin's private repository of student papers.
What happens to the document you upload to Copyleaks?
Read the Copyleaks privacy policy before uploading coursework. Two passages matter. First, the policy lists "to train our models" among the uses of submitted content, and says you can opt out at any time by contacting support at [email protected]. It also says Copyleaks will not use your credentials and contact details to train its models.
Second, the policy describes a Shared Data Hub. When it is enabled, scans are added to a database that other users' submissions are compared against. The policy says other users will only see the parts of your text that are identical to theirs, and that you can disable the feature and permanently delete files from the hub. If you are checking a draft you will later submit elsewhere, decide whether you want it in that database first.
Where Copyleaks is the better choice
Copyleaks does several things Plagino does not do at all. Be clear about these before you pick a tool on accuracy alone.
Web plagiarism and non-English text
If your main worry is text copied from websites, Copyleaks is the stronger tool, because it searches the open web and Plagino does not. It also checks plagiarism in 100+ languages, detects plagiarism translated from another language on its Pro plan, and runs AI detection in 30+ languages. Plagino is built around English academic drafts.
Institutions that need an LMS integration
Copyleaks plugs into seven learning management systems, syncs grades and feedback, and offers analytics at student, course and institution level. For a school that wants AI and plagiarism checks inside Canvas or Moodle, that matters more than a few points of detection rate. Plagino has no LMS integration.
Volume, formats and adjustable sensitivity
Copyleaks accepts pasted text, files, Google Docs and browser scans, handles images and source code, and lets enterprise users tune sensitivity to reduce false positives. Plagino takes a .docx file and nothing else. For a content team scanning many web pages, Copyleaks fits better.
Where Plagino is the better choice
Plagino is our tool, so weigh this section accordingly. On our benchmark it caught more AI-written documents than Copyleaks (97.4% against 91.3%) and wrongly flagged fewer human ones (0.8% against 2.2%), though the false-positive difference sits within the margin of error. For a student who wants to see which sentences an AI detector is likely to flag before a teacher runs one, that combination is the point.
The pricing model is also simpler for students. Plagino's Pro plan is $19 a month for 20 scans a day, rather than a word-based credit allowance, and the free plan gives 3 scans a month without a card. If you check one long dissertation chapter many times, a scan count can go further than 25,000 words of credits.
Whichever tool you use, a detector score is a signal, not proof. If you have been flagged, our guide for students who were falsely accused of using AI covers how to respond through your institution's process.
Test conditions and limitations
Our benchmark has real limits, and they apply to Plagino's own numbers as much as to Copyleaks'.
What the benchmark does not cover
The 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. We scored at document level, so a tool that flagged one sentence in an otherwise human essay counted as a false positive. We used default settings, which for Copyleaks means its "Balanced" sensitivity.
The sample is 500 documents per rate. That is enough to separate large gaps, such as Copyleaks' detection rate from Plagino's, but not small ones. The confidence intervals in the table show where a difference is real and where it is not.
False positives are uneven across writers
A single false-positive rate hides who gets flagged. A 2023 Stanford study found that several AI detectors misclassified more than half of TOEFL essays by non-native English writers as AI-generated. Turnitin itself says false positives are more common when a document contains less than 20% AI writing. Our guide to AI detector false positives explains why, and how to read a borderline score.
For other head-to-head results, see Plagino vs Originality.ai, Plagino vs Winston AI and Plagino vs Grammarly.
Frequently asked questions
Is Copyleaks AI detector accurate?
It is reasonably accurate but not as accurate as 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 testing reports a 0.30% false positive rate at its default setting.
Can Copyleaks give false positives?
Yes. Every AI detector does. Copyleaks wrongly flagged 2.2% of human-written documents in Plagino's benchmark, and its own testing reports false positives at all three sensitivity levels. A flag should prompt a conversation and a look at drafts, not be treated as proof.
Is Copyleaks free?
Partly. Copyleaks lets you scan up to 25,000 characters for AI without logging in, and a free account adds monthly credits. Paid plans start at $16.99 a month, or $13.99 a month billed annually, for 100 credits a month, where one credit covers up to 250 words.
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.
Does Copyleaks store my paper?
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 are added to a database that other users' submissions are compared against. The policy says you can disable it and permanently delete files from it.
Do universities use Copyleaks?
Some do. Copyleaks sells education plans priced by the number of full-time students and integrates with Canvas, Moodle, D2L Brightspace, Schoology, Sakai, Edsby and Blackboard. Whether your instructor uses it depends on your institution.