The tool loads your current browser's User-Agent string on open and breaks it down into browser name and version, operating system and version, device type (desktop, mobile or tablet) and rendering engine. You can also paste any UA string — for example one copied from a server log — and analyze it the same way. Detection uses a set of ordered regular-expression rules covering Chrome, Firefox, Safari, Edge, Opera, Internet Explorer and the common iOS and Android WebView cases.
Because so many browsers impersonate each other in the UA string (Chrome and Edge both contain "Safari", Edge contains "Chrome"), the rules are checked most-specific first so the real browser wins. UA sniffing is inherently approximate and easy to spoof, so treat the result as a best guess rather than proof. Everything runs locally in your browser and nothing is sent anywhere.