Copyleaks vs Turnitin, which AI detector is more accurate?

My school uses Turnitin but I have access to Copyleaks through another course. I ran the same set of papers through both to see how they compare.

Detection Accuracy

For clearly AI-generated text (unedited ChatGPT output), both tools performed similarly, catching it about 85-90% of the time. The real differences showed up with edge cases.

Turnitin was better at detecting AI content that had been lightly edited. Papers where I changed a few words and restructured some sentences still scored 70-80% AI on Turnitin but only 40-50% on Copyleaks.

For human-written content, Copyleaks had slightly fewer false positives in my testing. Turnitin flagged 3 out of 20 human papers while Copyleaks flagged 2 out of 20.

Scoring Differences

One thing that surprised me is how different the scores can be for the same paper. I had one essay score 45% AI on Turnitin and only 18% on Copyleaks. Another scored 12% on Turnitin and 31% on Copyleaks. There’s no consistency between the two tools.

Interface and Reporting

Turnitin gives you a clean, detailed report with highlighted sections and a similarity score alongside the AI score. Copyleaks has a similar interface but also shows sentence-level confidence which can be more granular.

Language Support

Copyleaks wins here with 30+ language support versus Turnitin’s more limited language detection. If you write in languages other than English, Copyleaks might be more useful for self-checking.

Which Should You Trust?

Neither should be trusted blindly. They use different models and different training data, which is why their scores often disagree. The best approach is to use whichever your school uses for self-checking, and keep records of your writing process as evidence in case of disputes.