A browser request field that identifies users to a server
What is a user agent?
A user agent is an HTTP browser request header that gives servers information regarding the client device and/or operating system on which the browser is running. A server’s response to a browser request typically changes depending on the device type. The information that the user agent may contain includes:
- application type
- operating system
- software vendor
- software version
Because user agents commonly manifest as browsers, they are relevant for both desktop and mobile web. In these case, the user is actively controlling the browser, while the browser is issuing UA strings that show the technology used for accessing web content. Below, you can see an example for both Android and iOS, respectively, running on mobile web:
- Mozilla/5.0 (Linux; Android 8.0.0; SM-G930F Build/R16NW) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/69.0.3497.91 Mobile Safari/537.36
- Mozilla/5.0 (iPhone; CPU iPhone OS 11_1_2 like Mac OS X) AppleWebKit/604.3.5 (KHTML, like Gecko) Version/11.0 Mobile/15B202 Safari/604.1
Why are user agents important for attribution?
Based on the above examples, it is clear that user agents provide much-needed information to identify users, as well as their devices. For this reason, user agents, along with IP addresses, are crucial for successful fingerprint matching when there is no unique identifier, like IDFA or Google Advertising ID (GAID), available to match between an ad interaction and an install action.