Copyleaks

An entry in the Humanizer Wiki directory of AI-text detectors.

Overview

Copyleaks is a long-running plagiarism-detection company that layered AI-content detection on top of its existing platform. The detector estimates the likelihood that a passage was machine-generated and supports multiple languages, which distinguishes it from many English-only tools. Its audience spans education, publishing, and enterprise content teams, and it exposes both a browser tool and an API for integration into other systems.

Accuracy in practice

Copyleaks states an accuracy figure around 99% with a false-positive rate near 0.2%, based on internal testing across a large sample set. Independent benchmarks published in 2025 and 2026 have reported a wider range of results depending on methodology, with strong performance on raw or lightly edited AI output and a steep decline on text that has been rewritten or run through a humanizer. As with all detectors, outputs are probabilistic, short samples are less reliable, and false positives, including for non-native English writing, remain a documented risk.

Summary

Copyleaks pairs an AI detector with mature plagiarism tooling and multilingual support, which makes it a common choice for organizations that already need both. Its scores are estimates rather than proof, and their reliability varies with text length and how much the content has been edited.

Humanizers vs. Copyleaks

How each humanizer we track has fared against Copyleaks, and when it was last tested. Full data in the effectiveness matrix.