Parse and analyze user agent strings to identify browser, OS, device type, and bot/crawler signatures.
A user agent string is what a browser sends to identify itself with every HTTP request - and it is not always truthful. Paste one into this tool and it breaks the string into its parts: browser and version, rendering engine, operating system, device class (mobile, tablet, desktop, or bot), and whether the string carries a known crawler signature such as Googlebot or Bingbot. The surprise most people hit: Chrome, Edge, and Opera all ship the same Mozilla/ and Safari/ prefixes as compatibility boilerplate, so the real browser is found in the Chrome/, Edg/, or OPR/ token, and the Safari version shown is always the frozen value 537.36.
A concrete input and expected output from the current implementation.
Input
Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/120.0.0.0 Safari/537.36
Expected output
Browser: Chrome 120.0.0.0 Rendering engine: Blink (the string itself claims AppleWebKit/537.36) Operating system: Windows 10 or later, 64-bit (Windows NT 10.0; Win64; x64) Device class: Desktop, no Mobile token Crawler: None detected
The Chrome/ token carries the real browser and version; Mozilla/5.0, AppleWebKit/537.36, and Safari/537.36 are compatibility tokens that every Chromium browser sends, so they identify nothing. Windows 11 also reports NT 10.0, which is why the OS is given as '10 or later' rather than a specific release.
A user agent string is a fixed-order sequence of tokens: a Mozilla/5.0 compatibility prefix, a parenthesized platform block (OS, architecture, sometimes device name), then engine and browser tokens such as AppleWebKit/537.36 and Chrome/120.0.0.0. The tool maps each token to a slot - platform, engine, browser, or crawler - and reports what each slot contains.
Device type is decided by markers: the Mobile token means a phone, iPad or Tablet means a tablet, and their absence means a desktop. Bot detection looks for crawler keywords (bot, spider, crawler), the (compatible; Name/version) form search engines use, and known crawler names. Both are heuristics: the string is self-reported, and a missing bot signature does not prove a human.
Chrome is right. Chromium browsers keep the AppleWebKit and Safari tokens their predecessor used so that websites sniffing for Safari will treat them as Safari. The version in those tokens is frozen - 537.36 in nearly every Chromium string - while the Chrome/ token carries the real browser and version.
Only the ones that identify themselves. Filtering on the UA string stops bots that honestly announce themselves, but it can also block real users on older browsers and misses any bot that copies a real Chrome string. Google and Microsoft publish verifiable IP ranges for their crawlers, and Google recommends reverse-DNS checks over trusting the string.
The example and behavioral notes were checked against the browser implementation. Standards and primary references below define the relevant format, formula, or platform behavior.
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