Why does Chrome's User-Agent mention Safari and Mozilla?

Purely for backward compatibility with servers that once sniffed for those tokens. The string is a chain of historical claims; only the later, browser-specific tokens are meaningful.

Can a User-Agent be trusted?

No. It is a self-reported string any client can set to anything, which is why it should never gate security decisions — and why bots routinely present as ordinary browsers.

What replaces the User-Agent header?

User-Agent Client Hints: a set of Sec-CH-UA headers a site can request, giving structured, granular data with less passive fingerprinting surface than one long string sent to everyone.

User-Agent Parser

Break a User-Agent string down into browser, engine, OS and device.

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RAW INPUT

DECODED

Output appears here as you type — decoded on your device.

Input is processed on your device. Nothing you paste is sent anywhere.

What is the User-Agent Parser?

A User-Agent parser interprets the User-Agent HTTP header — a string every browser sends identifying itself — extracting the actual browser, its version, the rendering engine and the operating system from a format thick with historical compatibility tokens.

User-Agent strings are an accident of history. Nearly every browser still begins with 'Mozilla/5.0' because early servers sniffed for it, and Chrome's string names Safari and KHTML for the same reason. The result is a header where almost every token is a compatibility claim rather than a fact, and parsing it means knowing which tokens to believe.

The reliable signals are the later ones: 'Chrome/120' before 'Safari' means Chrome; 'Version/17' before 'Safari' with no Chrome token means real Safari; 'Firefox/121' means Firefox; 'Edg/120' means Edge. Getting this wrong is how sites end up serving Safari-specific workarounds to Chrome.

The header is also being deliberately wound down. Chrome now freezes and reduces the detail it reports, moving to Client Hints (Sec-CH-UA headers) where sites request only what they need. Feature detection has always been the better approach; UA parsing remains useful for analytics, log analysis and bot identification.

User-Agent Parser at a glance

Header: User-Agent, sent on every HTTP request
Mozilla/5.0: A legacy compatibility token, not a real claim
Successor: User-Agent Client Hints (Sec-CH-UA)
Trustworthy?: No — trivially spoofed by clients and bots

How to use the User-Agent Parser

1Paste the User-Agent string from a log line or your browser's network tab.
2Read the identified browser, version, engine and operating system.
3Treat the result as a hint — the header is self-reported and freely faked.

When you would reach for it

Analysing which browsers and versions appear in your access logs.
Identifying bot and crawler traffic by its declared agent.
Reproducing a bug reported by a user who pasted their UA string.

User-Agent Parser — frequently asked questions

Last reviewed 25 July 2026 · questions or corrections: contact@decoder.tools