On the Web, a user agent is a software agent capable of and responsible for retrieving and facilitating end user interaction with Web content. This includes all common web browsers, such as Google Chrome, Mozilla Firefox, and Safari, some email clients, standalone download managers like youtube-dl, other command-line utilities like cURL, and arguably headless services that power part of a larger application, such as a web crawler.
The user agent plays the role of the client in a client–server system. The HTTP User-Agent header is intended to clearly identify the agent to the server. However, this header can be omitted or spoofed, so some websites use other agent detection methods.
See also edit
- "W3C Definition of User Agent". www.w3.org. 2011-06-16. Retrieved 2018-10-20.
- User agent at Mozilla web docs