Direct answer
Copyleaks runs an AI detector that scores text as human, AI-generated, or AI-generated + human edited. Paid plans start at $7.99 per month for 25,000 words and go up to enterprise contracts for API integrations. Copyleaks publishes a 99.1 percent accuracy figure on their own test set. Independent evidence suggests the same perplexity + burstiness limits that affect every mainstream detector apply here: paraphrased text, humanised text and writing by non-native English speakers all drive accuracy down. Strongest when bundled with Copyleaks' plagiarism scanner for publishing workflows.
Copyleaks began as a plagiarism scanner in 2015 and expanded into AI content detection in 2023. The detector is sold both standalone and as part of the plagiarism + AI combined scanner. This review covers what Copyleaks' detector actually measures, how its pricing compares to the other mainstream detectors, and where the public evidence suggests the score should and should not be trusted.
What Copyleaks measures
Copyleaks' AI detector returns a three-way classification: human, AI-generated, or AI-generated-plus-human-edited. The signal is the perplexity + burstiness class of classifier that every mainstream detector uses, with Copyleaks' own training-data tuning. The three-way output is a thoughtful UX improvement over the two-way scores most detectors return - "AI-edited" is a genuinely useful intermediate category - but the underlying signal is the same as Turnitin, Winston or GPTZero.
Pricing at a glance
| Plan | Monthly price | Monthly words | Headline feature |
|---|---|---|---|
| Standard | From $7.99 | 25,000 words | AI detection or plagiarism |
| Business | From $13.99 | 100,000 words | AI + plagiarism combined scanner |
| Enterprise / API | Negotiated | Volume contract | API, SSO, team governance |
Prices drawn from Copyleaks' public pricing page as of October 2026. Verify against the vendor site.
How we evaluated
We ran a batch of 25 passages through Copyleaks' free scan: 10 human-authored passages from before 2022, 10 GPT-4 class drafts from 2026, and 5 of those drafts after a pass through a cadence humaniser. We recorded Copyleaks' three-way classification for each. The sample is small; it is enough for the qualitative points below but not enough for an independent accuracy figure.
What we found
On raw GPT-4 passages Copyleaks returned the AI-generated classification consistently, matching the vendor's claim and the use case the tool is designed for. On human-written pre-2022 passages Copyleaks returned the human classification 9 of 10 times. On humanised passages Copyleaks typically returned the AI-edited-by-human intermediate classification, which is actually the honest answer: the text started as AI and was edited for structure, which is what the humaniser did. The three-way output here is a real improvement over the two-way score most detectors return.
The 99.1 percent accuracy figure Copyleaks publishes should be read as a vendor claim on a vendor-controlled dataset of raw AI text versus human text. On the real-world distribution of edited, paraphrased or non-native English text, every mainstream detector shows measurably lower reliability; the Stanford HAI 2023 study covers the general problem and the non-native English piece covers the writer-facing summary.
When Copyleaks is the right pick
- You already use Copyleaks for plagiarism scanning: the bundled AI detector is a reasonable add-on at a low marginal cost.
- You need the three-way human / AI / AI-edited classification: this is a UX advantage over the two-way scores most alternatives return.
- You need an API with SSO and enterprise support: Copyleaks' enterprise tier is more mature than most alternatives in this list.
- You accept the detector as a flag, not a verdict, and have a human escalation path for high scores.
Frequently asked questions
Is Copyleaks more accurate than Turnitin?
On vendor-published figures the gap is small (Copyleaks 99.1 percent versus Turnitin's claim of under 1 percent false positives). On independent testing both fail in similar patterns on paraphrased or non-native English text. The practical choice is usually driven by integration: Turnitin ships with university workflows, Copyleaks ships with publishing and content workflows.
Can Copyleaks detect humanised AI text?
Often, but the classification often shifts from AI-generated to AI-edited-by-human after a cadence humaniser pass. That intermediate classification is a feature, not a bug: it reflects what actually happened to the text. If a reviewer treats AI-edited as acceptable (which many editorial policies do), the humaniser pass is a successful one.
Does Copyleaks work for non-English text?
Copyleaks publishes support for multiple languages. Independent evaluation of detector accuracy on non-English text is thin; treat multi-language scores as directional rather than authoritative, particularly on languages with smaller training-data representation.