Definition
Plain language
Working out exactly which piece of software you're dealing with, from small quirks in how it behaves.
As stated in the literature
Identifying a specific implementation or version from observable behavioural differences (formatting quirks, default values, parsing edge cases) rather than from any declared identifier.
Also called: fingerprint, fingerprinted, fingerprints
Why it matters: Knowing the exact software and version in front of you is the step that turns a vague guess into a list of known weaknesses that actually apply.
For example, noticing that a service always trims the trailing space after a question can be enough to tell you which program is serving the model, even though it never says so.
Heard on the show
“Generates the hash values, which are these long alphanumeric fingerprints.”Episode 017 — When the Agent Grades Its Own Homework: A Brutal New Benchmark for AI Workers