A string of text sent by a device running Apple’s mobile operating system to identify itself to a server. This string contains information such as the operating system version, device model, and browser being used. An example would be: `Mozilla/5.0 (iPhone; CPU iPhone OS 15_0 like Mac OS X) AppleWebKit/605.1.15 (KHTML, like Gecko) Version/15.0 Mobile/15E148 Safari/604.1`.
This identifier plays a crucial role in ensuring websites and applications are rendered correctly and function optimally. Servers utilize the information to deliver content tailored to the specific device and operating system requesting it. This has historically been vital for adapting web experiences to the evolving capabilities and standards of mobile devices, resulting in improved user experience. Furthermore, it enables analytics and tracking, allowing developers to understand device usage patterns.