User Agent String

A User Agent String is a text identifier sent by web browsers, applications, or devices in HTTP headers to identify themselves to web servers. It typically includes details like the browser name, version, operating system, and rendering engine. This information helps servers deliver appropriate content, such as optimized web pages or device-specific resources.

Also known as: User-Agent, UA String, Browser String, HTTP User-Agent Header, Client Identifier

Why learn User Agent String?

Developers should understand User Agent Strings when building web applications that require browser detection, device targeting, or analytics. For example, it's used to serve mobile-optimized layouts, detect outdated browsers for compatibility warnings, or track usage statistics in web analytics tools like Google Analytics.

Learning Resources

• docs: MDN Web Docs: User-Agent
• tutorial: W3Schools: HTTP Header User-Agent
• docs: Google Developers: User-Agent Reduction
• video: YouTube: Understanding User Agent Strings
• tutorial: BrowserStack: Guide to User Agent Strings