Copyleaks AI Detector: We Tested It on English Texts

What Is Copyleaks?

Copyleaks is a long-established plagiarism detection company that added an AI detection module in 2023. Unlike Turnitin (which requires institutional access), Copyleaks is available to individual users and claims to support 30+ languages with high accuracy.

Our Test Methodology

We prepared 10 texts: 5 completely AI-generated (using ChatGPT-4 and Claude 3 Opus) and 5 entirely human-written across different genres — academic essay, news article, blog post, technical documentation, and creative writing. Each was submitted to Copyleaks without any modification.

Results: AI-Generated Texts

Copyleaks correctly identified 4 out of 5 AI-generated texts (80% accuracy). The one it missed was a Claude-generated piece that scored only 34% AI probability — below Copyleaks' flagging threshold. This suggests that different AI models produce detectably different output.

Results: Human-Written Texts

One human-written text out of five was falsely flagged as AI-generated (20% false positive rate). This occurred with a technical article written in a formal, consistent style — precisely the kind of writing that bumps against AI detection thresholds.

Copyleaks vs. Competitors

Copyleaks performs comparably to GPTZero on English text but falls below Turnitin's enterprise version. Its main advantage is multilingual support and accessibility to individual users without institutional licenses.

Verdict

Copyleaks is a solid tool but not infallible. For content you need to pass detection, using a humanization tool like Temiz Metin beforehand consistently reduces scores below detection thresholds across all major detectors.