---
title: "User-Agent"
description: "The line a browser or crawler sends with every request, naming itself. It is how a visit from GPTBot is told apart from a visit from a person."
topic: "Retrieval & Behavior"
canonical: "https://geordy.ai/glossary/retrieval-behavior/user-agent"
---
# User-Agent

The line a browser or crawler sends with every request, naming itself. It is how a visit from GPTBot is told apart from a visit from a person.

Every HTTP request carries a User-Agent header, a short self-declared string such as Mozilla/5.0 (compatible; GPTBot/1.2; +https://openai.com/gptbot). Bot analytics is built on it: match the string against a list of known crawlers and you know which AI system read which file and when. It is self-declared, so it can be faked, but the major AI operators publish their agent names precisely so publishers can recognise and control them. The same names appear on the User-agent lines in robots.txt.
---

Source: https://geordy.ai/glossary/retrieval-behavior/user-agent
This is a machine-readable markdown version of that page, generated by Geordy.