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Glossary Web & HTTP

User agent

A user agent is the software making a web request, such as a browser or crawler, which identifies itself to servers in the User-Agent header.

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In more detail

The header string names the browser, its version and the operating system, for example Mozilla/5.0 (Windows NT 10.0; Win64; x64) ... Chrome/130.0. Sites use it to adapt content and to recognise crawlers. It is easy to fake and, with browsers now reducing the detail they send, is an unreliable way to identify devices.

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User-Agent Parser

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See also

  • Glossary HTTP
    HTTP (Hypertext Transfer Protocol) is the protocol browsers and servers use to request and send web pages, files and data.
  • Cheat sheet HTTP Headers Cheat Sheet
    Request and response headers, Cache-Control directives, security headers, cookie attributes and CORS headers.
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