Can I trust what a user agent says?

No. It is a plain header the client sets, so anything can claim to be anything — one line of code changes it. Use it for analytics and for rough segmentation, never for security decisions or access control. A crawler that wants to look like Chrome simply says it is Chrome.

Why is the engine reported separately from the browser?

Because the engine is what determines behaviour. Chrome, Edge, Opera, Brave and Vivaldi are all Blink, so a bug in one is usually a bug in all of them. And on iOS, Apple requires every browser to use WebKit — so “Chrome on iPhone” is Safari's engine wearing Chrome's name, which is exactly the kind of thing that explains a bug that only reproduces on one device.

Should I use user agent sniffing in my code?

Almost never. Feature detection — checking whether the thing you need exists — is accurate, doesn't break when a new browser ships, and doesn't need a table of strings maintained forever. Reserve user agent parsing for analytics, and for genuine per-device workarounds you have no other way to detect.

User Agent Parser

Paste a user agent string from a log file and find out what it actually is. Every browser's user agent is a pile of historical lies — Chrome claims to be Safari, which claims to be Gecko, which claims to be Mozilla, all because sites once sniffed for a competitor and served a worse page. This unpicks that, reporting the rendering engine separately from the brand name, because the engine is what decides whether your CSS works.

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Result

Nothing is uploaded — this tool runs inside your browser, so your files never leave your device.

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Why use this tool

Browser and version, resolved in the right order so Edge isn't read as Chrome
Rendering engine reported separately — on iOS everything is WebKit
Operating system, version and device type: desktop, mobile, tablet, TV or console
Flags crawlers, scripts and headless browsers

How it works

1Paste the user agent string from your server log or analytics.
2Read the breakdown — browser, engine, OS and device.
3Check the note if it's flagged as automated.

User Agent Parser — frequently asked questions

Pure historical accident. Netscape called itself Mozilla; Internet Explorer added it to get past sites that checked for Netscape; Safari added Gecko-compatible tokens; Chrome copied Safari's. Every step was a browser pretending to be its predecessor to avoid being served a degraded page, and none of it can be removed now without breaking sites that still sniff for those strings.

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