User agent
User agent
User agent definition
A user agent is a type of software that acts as an intermediary between a user and a network service, like a website. It sends requests for data or resources on behalf of the user and communicates with servers to accomplish this task. Any client-side software that interacts with servers over a network can be considered a user agent.
See also: application client, application program, application layer
User agent types
- Web browsers. The most common type of user agent, web browsers like Google Chrome or Mozilla Firefox, interact with web servers to display web pages to the users.
- Email clients. Applications like Microsoft Outlook or Apple Mail act as user agents by communicating with email servers to send and receive emails on behalf of the user.
- News readers. Services like Feedly or NewsBlur fetch news feeds from various sources and present them in a user-friendly format.
- Web crawlers or bots. These user agents are operated by search engines like Google or Bing. They scour the internet, indexing web content to make it searchable.
- API clients. These are software applications that communicate with servers via APIs (Application Programming Interfaces). These can include mobile apps, desktop apps, and server applications.
- Accessibility tools. User agents such as screen readers are designed to help people with disabilities browse the web.
- Download managers. These user agents, like Internet Download Manager, help users download files from servers, often providing features like pause and resume and faster download speeds.