User Agent

Full Title or Meme

A digital Entity that is operating at the consent and authority of the user.

The best User Agent on an internet connected device is a User Trusted Browser to work only in the user's best interests.
When discussing the use of the internet by a user, what is really meant is the presence of the user's agent on an internet connection.
Typically the Native App will run on a User Device in the user's physical possession, but it is possible that the agent is running on a service in The Cloud. Usually this would not be detected by a Web Site.

Nearly any application running on a user's device is allowed to access the internet and claim that it represents the user. There is no built-in mechanism to test this assertion by an internet connected service. The internet was designed to connect computer systems, and that is all it can be relied upon to do.
Any Web Site that wishes to create a Persistent Identifier for a User will need to take responsibility for any necessary Assurance that the program running on the user's device really does reflect the will of the user.
Most of the larger enterprises operating on The Web prefer to supply a Native App to the users device to improve the User Experience for that site.
To be sure that the User Agent really is operating on the user's behalf, the Web Site needs to know the level of Assurance that can be assigned to the user's device as well as the User Agent.

The most common way for Users to access a Web Site is with a web browser from some well-know browser provider either within a device operated by the user, or on a cloud computer under user control.
While current web browsers do allow Web Sites to include programs as JavaScript to run within the browser, they do provide a very restricted Sandbox where the script must run for security reasons.