User Agent

What Does User Agent Mean?

A user agent (UA) is a software element that acts on behalf of a user. However, the term user agent has also come to be associated with a header string in HTTP and related technologies that help a hosting server identify the type of operating system and/or device requesting content.


The use of user agents is a controversial topic because of UA requests for Web content and the creation of Web pages that handle various browsers in different ways. A movement to equalize access between browsers attempted to promote more broadly accessible design, but some sites are still designed with specific browsers or devices in mind. In general, the browser as UA is a key component of the Internet’s developmental timeline. It continues to change as desktop and laptop computers give way to mobile devices for Internet viewing.

Techopedia Explains User Agent

A broader UA definition includes Web crawlers, Web bots and other technologies. However, a Web browser is a simple example of a common UA setup. Here, the browser acts as the UA, where the user actively controls the browser. The browser issues certain UA strings that show the specific technology used to access a site, page or other content. For example, a UA string from a Firefox browser would include the word Mozilla, as well as version data and other details.


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Margaret Rouse

Margaret Rouse is an award-winning technical writer and teacher known for her ability to explain complex technical subjects to a non-technical, business audience. Over the past twenty years her explanations have appeared on TechTarget websites and she's been cited as an authority in articles by the New York Times, Time Magazine, USA Today, ZDNet, PC Magazine and Discovery Magazine.Margaret's idea of a fun day is helping IT and business professionals learn to speak each other’s highly specialized languages. If you have a suggestion for a new definition or how to improve a technical explanation, please email Margaret or contact her…