Paste a user agent string and extract browser, OS, device type, and rendering engine details.
A user agent string is the line a browser sends in its HTTP User-Agent header, and this tool unpacks it into labeled parts: browser family and version, operating system, device type (desktop, phone, tablet), and rendering engine. Paste the string, read the breakdown. Handy when a server log or analytics report shows a client you do not recognize. Parsing happens in the page; nothing you paste is uploaded. The surprise: the string is half compatibility theater. Browsers embed tokens borrowed from other browsers, freeze their OS version at an old value, and keep the real browser version in a less obvious token. The parse follows the conventions; the string itself misleads.
A concrete input and expected output from the current implementation.
Input
Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/605.1.15 (KHTML, like Gecko) Version/17.4 Safari/605.1.15
Expected output
browser: Safari 17.4 engine: WebKit 605.1.15 os: macOS 10.15.7 (Catalina) device: Desktop (Mac)
Version/17.4 is the browser version token while Safari/605.1.15 repeats the WebKit build number, so the parse reports Safari 17.4 with engine WebKit 605.1.15. The parenthesized segment gives macOS 10.15.7 (10_15_7 uses underscore separators) on a desktop Mac, and the Mozilla/5.0 and like Gecko tokens are compatibility leftovers that are ignored.
A UA string is a product token, a platform segment in parentheses, and product-pair tokens. The parser assigns the browser from the product tokens (Safari, Chrome, Firefox, Edge), the OS from the platform segment (Mac OS X 10_15_7, Windows NT 10.0), and the engine from the AppleWebKit or Gecko token. Mozilla/5.0 and like Gecko are compatibility tokens, ignored rather than reported as a Mozilla browser.
Several tokens carry version numbers, and parsers apply precedence. In Safari strings, Version/17.4 holds the browser version while Safari/605.1.15 holds the WebKit build; in Chromium strings the trailing Safari/537.36 token is a stub and must be ignored. When nothing matches, the browser or OS is reported as unknown rather than invented. Platform versions with underscore separators (10_15_7) are normalized to dotted form (10.15.7).
It should not. The 604.1 in Mobile/15E148 Safari/604.1 is a legacy build number iOS Safari has kept frozen for years; the real browser version is in the Version token, so Version/17.4 parses to Safari 17.4. If your logs show 604.1, that parser is reading the Safari token instead. The OS comes from iPhone OS 17_4 in the platform segment.
No. The tool identifies what the string claims, and bot traffic often claims to be a browser: headless Chrome sends the same UA as desktop Chrome, and scrapers can copy any string. Some bots label themselves (Googlebot, bingbot) and may be named accordingly, but nothing in a UA proves what is behind it, so treat any bot determination as a hint rather than a verdict.
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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