9 October 2023
Last modified: 15 March, 2022
A user agent string is a string of data that browsers send when requesting content from websites or ad servers. The data contains information on the browser, such as version, device type, and operating system, and when the website or ad servers receives the request, it is able to return content or ads that will render correctly – for example, serving mobile-optimised content to a mobile device.
User-agent spoofing is a form of fraud where the string of data is modified to provide false information or hide details – for example, a bot making multiple automated requests for content from a single device could modify the user agent string to pretend those requests (and the resulting impressions) are from multiple devices.