Copyleaks Review

Copyleaks is an AI content detector and plagiarism checker that scans text, images, and source code for machine-generated or copied material. Operated by Copyleaks Ltd and founded in 2015, the company is headquartered in Stamford, Connecticut, with research and development based in Israel. Copyleaks scores content through a machine learning model that reads linguistic patterns, sentence structure, and word probability to separate human writing from AI output, then pairs that classifier with source matching for plagiarism.

Copyleaks runs AI detection across 30+ languages and plagiarism scanning across 100+ languages, exposing both through the web app, a REST API, and a Chrome extension. The AI detector returns a passage-level probability rather than a single document score, so mixed human and AI documents show exactly which sections triggered detection. Beyond text, Copyleaks extends into AI image detection, source code detection through Codeleaks, text moderation, and an AI Grader for rubric-based scoring of student writing.

Accuracy and false positives

Copyleaks advertises 99%+ AI-detection accuracy with a 0.03% false-positive rate. Those are vendor figures rather than independently confirmed results, and independent 2025 testing places Copyleaks among the stronger detectors while still recording lower raw accuracy and a 10 to 30 point drop on edited or paraphrased text. False positives tend to cluster on formulaic phrasing and non-native English, which the classifier reads as machine-like, so Copyleaks recommends human review of any flagged passage before an academic or employment decision.

Copyleaks bills paid usage on a credit model, where 1 credit covers up to 250 words of text or 1 image, credits reset monthly, and unused credits do not roll over. A limited free tier covers AI detection only, capped at roughly 2,500 words, while plagiarism scanning, image detection, source code detection, and text moderation all require a paid credit plan. Copyleaks holds SOC 2 Type II, SOC 3, PCI DSS, and GDPR compliance and encrypts submitted content in transit and at rest, though users handling sensitive work should confirm the current data-retention terms first.