It is an HTTP header sent by the browser with every request, in the format: "BrowserName/Version (OS; Architecture) Compatibility/1.0 Engine/Version". The syntax is defined by RFC 7231 and was originally created so servers could adapt responses for different clients.
User Agent Parser
Understand what your browser says about itself
The HTTP header that identifies the client — and its modern limitations
The HTTP User-Agent header is a string sent by the browser in every request, identifying the client software (name, version, engine, OS). It is widely used for analytics, feature detection and compatibility. However, modern browsers have progressively reduced UA detail to protect user privacy — a process called User-Agent Reduction (Chrome) with similar approaches in Firefox and Safari. As a replacement, the W3C proposes the User-Agent Client Hints API, which lets servers request only the data they actually need.
Detect or paste any UA
- Click "Detect my UA" to automatically analyse the current browser. The User-Agent string is read from navigator.userAgent.
- Or paste any User-Agent string in the text field — useful for testing UAs from other devices or browser versions.
- Results show the browser, version, rendering engine, operating system and device type extracted from the string.
Sources and references for this tool
These references help contextualize formulas, standards, APIs and limitations used on this page. They do not replace professional validation when a result has legal, financial, medical or operational impact.