Grammarly's AI detector offers a user-friendly way to check for AI-generated content but is not highly accurate compared to specialized AI detectors. It works by analyzing language patterns and sentence structures to provide an AI content likelihood percentage but struggles with complex, short, or heavily paraphrased text. Tests show it often underestimates AI presence, especially in mixed or humanized AI content, and can sometimes falsely flag human writing as AI. While integrated seamlessly in Grammarly's platform, it's best used as a supplementary tool rather than a definitive AI content detector, and users often need to double-check with more advanced detectors for higher accuracy. Overall, Grammarly's AI detector is more conservative, with false negatives and occasional false positives being common.