User-Agent

RequestActive

The User-Agent header identifies the client software making the request. Servers use it for browser detection, analytics, and sometimes content negotiation. It contains the application name, version, and operating system. Modern clients send long multi-token strings due to historical browser compatibility reasons.

User-Agent: <product>/<version> (<comment>) <product>/<version>...

Description

The User-Agent request header is a characteristic string that lets servers and network peers identify the application, operating system, vendor, and/or version of the requesting user agent.

Examples

Chrome on macOS

http

User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/120.0.0.0 Safari/537.36

API client

http

User-Agent: MyApp/2.1.0 (api-client; +https://example.com)

curl

http

User-Agent: curl/8.4.0

Specification

RFC 9110 – User-Agent specification →