In computing, a user agent is software (a software agent) that is acting on behalf of a user. For example, an email reader is a Mail User Agent, and in the Session Initiation Protocol (SIP), the term user agent refers to both end points of a communications session.
In many cases, a user agent acts as a client in a network protocol used in communications within a client–server distributed computing system. In particular, the Hypertext Transfer Protocol identifies the client software originating the request, using a "User-Agent" header, even when the client is not operated by a user. The SIP protocol (based on HTTP) followed this usage.
Read more about User Agent: User-agent Identification, User Agent Spoofing, User Agent Sniffing, Encryption Strength Notations
Famous quotes containing the words user and/or agent:
“A worker may be the hammer’s master, but the hammer still prevails. A tool knows exactly how it is meant to be handled, while the user of the tool can only have an approximate idea.”
—Milan Kundera (b. 1929)
“The agent never receipts his bill, puts his hat on and bows himself out. He stays around forever, not only for as long as you can write anything that anyone will buy, but as long as anyone will buy any portion of any right to anything that you ever did write. He just takes ten per cent of your life.”
—Raymond Chandler (1888–1959)