What is a User-Agent string?

A User-Agent (UA) is an HTTP header sent by browsers and apps to identify themselves to web servers. It typically includes the browser name and version, rendering engine, operating system, and device information.

How do I find my current browser's User-Agent?

The tool automatically shows your current browser's User-Agent when the page loads. You can also type javascript:alert(navigator.userAgent) in your address bar, or look in DevTools → Network → any request → Request Headers → user-agent.

Why do User-Agent strings look so complex?

UA strings are complex for historical reasons: each new browser added tokens from previous browsers to ensure backward compatibility with server-side detection scripts. For example, Chrome includes "Mozilla/5.0", "AppleWebKit", "Safari", and "Chrome" all in the same string.

What is the difference between mobile and tablet detection?

Mobile detection looks for "Mobile" in the UA string, which Android phones include but Android tablets do not. iPads no longer include "iPad" by default in modern iOS (they show a Mac UA instead), making tablet detection increasingly unreliable from the UA string alone.

Can I trust User-Agent detection to serve different content?

User-Agents can be spoofed. For feature detection, use JavaScript APIs (navigator.maxTouchPoints, CSS media queries) rather than UA sniffing. UA parsing is most useful for analytics and debugging, not for access control.

What is the Blink rendering engine?

Blink is the rendering engine used by Chrome, Edge, Opera, Brave, and most other modern browsers. It was forked from WebKit (used by Safari) in 2013. Firefox uses Gecko, and Safari uses WebKit.

What does the "Gecko/20100101" token mean in Firefox UA strings?

The "20100101" date is a frozen compatibility token — it does not represent the actual Firefox build date. It was frozen to prevent server-side scripts from using the date to sniff Firefox versions.

Is this User-Agent sent to any server?

No. The parsing happens entirely in your browser using JavaScript regular expressions. The UA string you paste never leaves your device.

Web Tools /

User agent parser

Paste any User-Agent string to decode browser, operating system, device type, and rendering engine. Your current UA is pre-filled below.

100% in your browser. User-Agent strings are never sent to any server.

User-Agent string

How to use

Your current browser's User-Agent string is pre-filled automatically.
Or paste any UA string you want to analyse — e.g. from server logs or a mobile device.
Results appear instantly as you type or paste.
Click Use my UA to restore your own browser's string.

Common use cases

Analytics debugging — identify which browser or OS is misclassified in your analytics.
Log analysis — parse UA strings from server access logs to understand visitor breakdown.
Testing — confirm which UA string a headless browser or crawler is sending.
Bot detection — identify crawlers like Googlebot, Bingbot, or scrapers.

Also see: IP Info Lookup and HTTP Status Reference.

常見問題

What is a User-Agent string?: A User-Agent (UA) is an HTTP header sent by browsers and apps to identify themselves to web servers. It typically includes the browser name and version, rendering engine, operating system, and device information.
How do I find my current browser's User-Agent?: The tool automatically shows your current browser's User-Agent when the page loads. You can also type javascript:alert(navigator.userAgent) in your address bar, or look in DevTools → Network → any request → Request Headers → user-agent.
Why do User-Agent strings look so complex?: UA strings are complex for historical reasons: each new browser added tokens from previous browsers to ensure backward compatibility with server-side detection scripts. For example, Chrome includes "Mozilla/5.0", "AppleWebKit", "Safari", and "Chrome" all in the same string.
What is the difference between mobile and tablet detection?: Mobile detection looks for "Mobile" in the UA string, which Android phones include but Android tablets do not. iPads no longer include "iPad" by default in modern iOS (they show a Mac UA instead), making tablet detection increasingly unreliable from the UA string alone.
Can I trust User-Agent detection to serve different content?: User-Agents can be spoofed. For feature detection, use JavaScript APIs (navigator.maxTouchPoints, CSS media queries) rather than UA sniffing. UA parsing is most useful for analytics and debugging, not for access control.
What is the Blink rendering engine?: Blink is the rendering engine used by Chrome, Edge, Opera, Brave, and most other modern browsers. It was forked from WebKit (used by Safari) in 2013. Firefox uses Gecko, and Safari uses WebKit.
What does the "Gecko/20100101" token mean in Firefox UA strings?: The "20100101" date is a frozen compatibility token — it does not represent the actual Firefox build date. It was frozen to prevent server-side scripts from using the date to sniff Firefox versions.
Is this User-Agent sent to any server?: No. The parsing happens entirely in your browser using JavaScript regular expressions. The UA string you paste never leaves your device.

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