User-agent
HTTP request header that identifies the crawler or client (e.g. GPTBot, ClaudeBot); used in robots.txt rules and analytics.
Definition
The User-agent (or User-Agent) is an HTTP request header that identifies the client making the request: browser name and version, or crawler name (e.g. GPTBot, ClaudeBot, PerplexityBot, Google-Extended). In robots.txt, rules are defined per User-agent so you can allow or disallow specific crawlers. In server logs and analytics, filtering by User-agent lets you measure which AI crawlers visit your site and which pages they request.
Relevance to GEO
Correctly configuring robots.txt by User-agent controls which AI crawlers may access your content. Tracking User-agent in logs helps you monitor GEO effectiveness and crawl patterns.