Question 1

What is a User-Agent string?

Accepted Answer

A User-Agent (UA) string is a text identifier sent by browsers and HTTP clients in the User-Agent request header. It describes the browser name and version, the operating system, and sometimes the device, so servers can tailor responses or collect analytics.

Question 2

How does the User-Agent parser work?

Accepted Answer

The parser applies a set of regular expressions to the UA string to extract browser name and version, operating system, device type and model, and rendering engine. It works entirely in your browser — no UA is ever sent to a server.

Question 3

Can I trust the User-Agent string?

Accepted Answer

Not fully. Browsers can spoof UA strings (e.g. via DevTools or extensions), and some browsers freeze or reduce the UA for privacy. Use UA parsing for analytics and progressive enhancement, never for security or authentication.

Question 4

What is UA Client Hints?

Accepted Answer

User-Agent Client Hints (UA-CH) is a modern privacy-friendly replacement for the UA string. Browsers send structured headers like Sec-CH-UA instead of a long UA string, giving sites only the data they actually need.

🔍 User-Agent Parser

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Recent UA strings (stored locally)