DevToolbox

User-Agent Parser

A User-Agent string is a line of text that browsers and other HTTP clients send with every request, identifying themselves to the server. These strings are notoriously dense and hard to read by eye, packed with historical compatibility tokens. This parser breaks a User-Agent string down into readable fields — browser name and version, rendering engine, operating system, and device type.

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Your data stays in your browser — this tool runs entirely on the client side and nothing is uploaded to a server.

How to Use the User-Agent Parser

  1. Click "Use My Browser" to parse your own current User-Agent automatically, or paste any User-Agent string manually.
  2. The parsed browser, engine, OS, and device details appear immediately.
  3. Use this to debug analytics data, browser-detection logic, or support tickets that include a raw UA string.

Why User-Agent strings look so strange

For historical compatibility reasons, nearly every browser's User-Agent string contains the token "Mozilla/5.0," regardless of whether it has anything to do with the original Mozilla browser. This dates back to a period when websites checked for that token to decide whether to serve advanced content, and browsers kept including it to avoid being blocked by that old logic.

Reliability considerations

User-Agent strings are self-reported by the client and can be changed or spoofed freely. They should never be used as a security mechanism. Additionally, newer browser privacy initiatives are gradually reducing how much detail is exposed in the User-Agent string by default, so feature detection is generally a more reliable approach than User-Agent sniffing for critical functionality.

Example

Example UA string
Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/120.0.0.0 Safari/537.36
Browser: Chrome 120 · Engine: Blink · OS: Windows 10/11 · Device: Desktop

Tips

  • Never rely on User-Agent sniffing for security decisions — it can be trivially spoofed.
  • Prefer feature detection (checking if an API exists) over browser detection where possible.

Frequently Asked Questions

Can a User-Agent string be faked?

Yes, easily — any client can send any User-Agent string it wants, including browser developer tools with a single click.

Why do all browsers say "Mozilla"?

It's a historical compatibility token, not an indication that the browser is actually Mozilla-based.

Related Tools

HTTP Status Code Reference Searchable reference of HTTP status codes and their meanings. MIME Type Lookup Look up the MIME type for a file extension, or vice versa.