User Agent

This basically tells you what type of device and what browser someone’s using. It provides more info, but this is the gist of it. See the MDN docs for more info.

Here’s an example:

Mozilla/5.0 (Linux; Android 10; K) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/114.0.0.0 Mobile Safari/537.36

This is a user agent representing Chrome on a phone running Android 10.