GPTZero

GPTZero is a leading AI-content detector built to identify whether text was written by a human or generated by AI tools like ChatGPT, Claude or Gemini. As generative AI flooded classrooms and workplaces, GPTZero became one of the most recognized tools for educators, publishers and hiring managers wanting to know if writing is authentically human — analyzing text for the statistical patterns (like "perplexity" and "burstiness") that tend to distinguish machine writing from human writing.

It highlights which specific sentences are likely AI-generated, provides an overall probability score, and offers features for educators including a dashboard, writing-process replay (showing how a document was actually written over time), and batch scanning. There are browser extensions, an API for developers, and integrations for institutions.

The free plan allows limited scans with word-count caps. Paid plans (Essential, Premium and organizational tiers, from around $10–$23/month) raise limits, unlock advanced detection, plagiarism checking and team features.

Strengths: one of the more reputable detectors, useful diagnostic features like writing replay, and constant model updates as AI evolves. Weaknesses — and these are important — no AI detector is reliable enough to be definitive: GPTZero can produce false positives (flagging human writing, especially from non-native English speakers) and false negatives (missing lightly edited AI text). Its results should inform a conversation, never serve as sole proof of misconduct.

For teachers, editors and organizations wanting a first-pass signal on AI-generated content, GPTZero is among the best available — used responsibly, as guidance rather than a verdict.