AI detection tools do not search a database of AI-generated text. Instead, they calculate statistical probability based on word predictability.

The Two Metrics Behind AI Detectors

  • Perplexity: A measure of word choice randomness. LLMs choose predictable words; human writing exhibits higher perplexity.
  • Burstiness: Variation in sentence length and structure. Humans naturally vary sentence length, while AI outputs uniform sentence sizes.