What is my user agent?
Mozilla/5.0 AppleWebKit/537.36 (KHTML, like Gecko; compatible; ClaudeBot/1.0; +claudebot@anthropic.com)
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216.73.216.229 Connection
- HTTP/2 Protocol
The HTTP version your browser and this server agreed on. HTTP/3 runs over QUIC and is the newest of the three.
- TLSv1.3 TLS
The version of transport encryption protecting this connection. TLS 1.3 is current; anything below 1.2 is obsolete.
- IPv4 IP version
IPv4 addresses are four numbers; IPv6 addresses are eight groups of hexadecimal digits. Both run at the same time and your browser picks whichever both ends support.
- Columbus Served from
The Cloudflare data centre that served this page. It is the closest one on the network, which is not always the closest one geographically.
Device
- — Browser language
The language your browser asks for, taken from your operating system. Sites use it to choose which version to show you.
- — Screen
Your screen size in pixels, readable by any script on the page without asking. It is one of the values that make up a browser fingerprint.
- — Browser time zone
The time zone your operating system is set to. It does not change when you connect a VPN, which is why comparing it with the one above catches leaks.
Mozilla/5.0 AppleWebKit/537.36 (KHTML, like Gecko; compatible; ClaudeBot/1.0; +claudebot@anthropic.com)
Every request your browser makes carries a user agent — a short self-description of the browser, its version and the platform it runs on. It is one of the oldest headers on the web and one of the most quietly informative.
Why the string looks like nonsense
A modern user agent reads like an archaeological dig: Mozilla/5.0 at the front, a rendering engine in the middle, several browser names that may or may not apply. The reason is straightforward. When servers began checking the string to decide which version of a page to send, any browser that did not claim to be the popular one got the degraded page. So every browser started claiming to be every other browser, and the strings never got shorter.
Browsers are now reducing what they report. Chrome freezes most of the detail and offers precise values only to sites that explicitly ask through Client Hints; Safari has reported a near-constant string for years.
What else your browser announces
The user agent is only part of what goes out without asking:
- Language — from
Accept-Language, driving both the site’s language choice and a fingerprint. - Screen size and pixel density — read by any script on the page.
- Time zone — from your operating system, and a reliable cross-check against your IP address.
- Platform hints — CPU architecture, mobile or desktop, device memory.
Fingerprinting, briefly
No single value identifies you. Taken together they often do. A particular browser version, on a particular operating system, at a particular resolution, in a particular time zone, with a particular font set, is frequently unique across millions of visitors — and unlike cookies, there is nothing to clear.
Faking one value usually makes things worse: a user agent claiming Windows on a machine that renders like a Mac is far more distinctive than either honest answer.
Frequently asked questions
What is a user agent string?
A line of text your browser sends with every request, naming itself, its version and the operating system. Servers use it to decide what to send you.
Why does it mention browsers I do not use?
Historical compatibility. Nearly every user agent claims to be Mozilla and most claim Safari or Chrome as well, because decades of server-side sniffing rewarded browsers that pretended to be their competitors.
Can I change my user agent?
Yes, browsers and extensions let you set it freely. It rarely helps privacy: an unusual string makes you more distinctive, not less, and everything else about your browser still matches.
Is a user agent enough to identify me?
Not on its own. Combined with screen size, language, time zone, installed fonts and rendering behaviour, it contributes to a fingerprint that is often unique across millions of visitors.