Parse any User-Agent string to detect browser, operating system, device type, rendering engine, and bot status — instantly in your browser.
| Bot | Purpose | Identifier |
|---|---|---|
| Googlebot | Google Search crawler | Googlebot |
| Bingbot | Bing Search crawler | bingbot |
| GPTBot | OpenAI web crawler | GPTBot |
| ClaudeBot | Anthropic web crawler | ClaudeBot |
| Slurp | Yahoo crawler | Slurp |
| DuckDuckBot | DuckDuckGo crawler | DuckDuckBot |
| Baiduspider | Baidu crawler | Baiduspider |
| YandexBot | Yandex crawler | YandexBot |
| facebookexternalhit | Facebook link preview | facebookexternalhit |
| Twitterbot | Twitter/X link preview | Twitterbot |
A User-Agent string is an HTTP header that identifies the client (browser, bot, or app) making a request. This tool parses any UA string to extract browser name, version, operating system, device type, rendering engine, and bot detection — all without sending data to any server.
A typical Chrome UA string looks like:
Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/124.0.0.0 Safari/537.36
The Mozilla/5.0 prefix is historical — nearly all browsers include it for compatibility. The actual browser identity comes from tokens like Chrome/124.0.0.0.
Modern browsers are moving toward User-Agent Client Hints (UA-CH), which provide structured, lower-entropy data via HTTP headers like Sec-CH-UA, Sec-CH-UA-Platform, and Sec-CH-UA-Mobile. However, the traditional UA string remains widely used and supported.
Use our Robots.txt Generator to create crawl rules for search engines and AI bots.
Generate Robots.txt →A User-Agent string is a text identifier sent by browsers and apps in HTTP request headers. It contains information about the browser name and version, operating system, rendering engine, and device type. Servers use this to deliver browser-specific content or log analytics.
This is a legacy compatibility artifact. Netscape/Mozilla was the dominant browser in the 1990s, so servers checked for 'Mozilla' to serve full-featured pages. Other browsers adopted the prefix to receive the same content. Internet Explorer started using it, then WebKit, then Chrome. The result is every browser claiming to be Mozilla for backwards compatibility.
User-Agent sniffing means checking the User-Agent string to decide what code to run or content to serve. It's unreliable because User-Agent strings can be spoofed, are inconsistent across versions, and browsers regularly update them. Feature detection using JavaScript APIs like CSS.supports() is the recommended alternative.
In Chrome DevTools, open the Network Conditions tab and uncheck 'Use browser default' under User agent, then type any UA string. Firefox has a similar option in developer settings. Browser extensions like User-Agent Switcher can toggle between presets. Developers use this to test how sites render for different browsers or devices.
User-Agent Client Hints (UA-CH) replaces the traditional User-Agent header with a privacy-preserving structured API. Instead of sending a full UA string with every request, browsers send minimal data by default and servers must explicitly request additional details via Accept-CH response headers. This reduces passive fingerprinting while still allowing legitimate browser detection.