User Agent

User agents are defined in the HTTP Header by user-agent strings, which often list the specific browser, with the version, as well as the device and/or host operating system that the browser will work on. User agents can also be bots and other software that emulate individual users. Google has published a list of their popular User Agent Strings for devices here: and a list of common GoogleBot User Agent Strings here:

Related Terms:

Mobile-First Indexing
Mobile First Design