User Agent Parser
Detect browser, OS, device type, and bot status from any user agent string.
Detect browser, OS, device type, and bot status from any user agent string.
A user agent (UA) string is a text identifier that your browser sends to every website you visit. It tells the server what browser you are using, which operating system you are on, and what rendering engine powers your browser. This information helps websites deliver the right version of their content, whether that means serving a mobile layout, applying browser-specific CSS fixes, or blocking incompatible features.
A typical user agent string looks something like: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/131.0.0.0 Safari/537.36. Despite looking cryptic, each segment carries meaning. The Mozilla/5.0 prefix is a historical artifact kept for compatibility. The parenthetical section describes the operating system. The remaining tokens identify the rendering engine and browser version.
Search engine crawlers identify themselves through user agent strings. Googlebot, Bingbot, and other crawlers each have distinctive UA signatures that website owners can use to identify crawler traffic in their server logs. This is important for SEO because it lets you verify that search engines can access your content and see how they interact with your pages.
Many websites serve different content based on user agent detection. While Google recommends responsive design over user agent-based serving, some sites still use UA sniffing to redirect mobile users or serve different page versions. If your site does this, it is critical to test how Googlebot and other crawler UAs are handled to ensure search engines see the same content as your users.
Identifying bots in your traffic is essential for accurate analytics and security. Legitimate crawlers like Googlebot, Bingbot, GPTBot, and others include identifying tokens in their user agent strings. This tool checks for common bot signatures including search engine crawlers, AI training bots, social media preview fetchers, and SEO tool crawlers.
Keep in mind that user agent strings can be spoofed. A malicious bot can send any user agent it wants, including one that mimics a real browser. For critical bot detection, user agent analysis should be combined with other signals like IP verification, behavior analysis, and rate limiting. However, for general analytics filtering and understanding your traffic composition, UA-based bot detection provides a solid starting point.
Your user agent string is one component of your browser fingerprint, a combination of technical details that can be used to identify your browser across websites. Other fingerprinting signals include screen resolution, installed fonts, timezone, language settings, and WebGL capabilities. Together, these create a surprisingly unique identifier.
Modern browsers are taking steps to reduce fingerprinting surface area. Chrome has been working on reducing the information in user agent strings through the User-Agent Client Hints API, which gives sites the basic information they need while requiring explicit requests for more detailed data. Firefox and Safari have also implemented various anti-fingerprinting measures. Understanding what your user agent reveals is a first step toward managing your online privacy.
This tool reads the navigator.userAgent property from your browser using JavaScript. This is the same string your browser sends to every website you visit in the HTTP request headers. The detection runs entirely in your browser with no server requests, so your user agent string is never transmitted or stored anywhere.
Yes. Use the Parse Custom User Agent input field to paste any user agent string you want to analyze. You can also click the common examples to quickly load user agents for Chrome on Windows, Safari on iPhone, Googlebot, GPTBot, BingBot, and Firefox on Linux. This is useful for testing how your site handles different browsers or for analyzing crawler strings from your server logs.
User agent parsing with regex is generally reliable for major browsers and operating systems, but it has limitations. Browsers sometimes include misleading tokens for compatibility reasons, such as Chrome including Safari in its UA string. Less common browsers or heavily customized user agents may not be detected accurately. For most practical purposes including analytics, bot detection, and browser compatibility checks, regex-based parsing provides good accuracy.
A bot (also called a crawler or spider) is an automated program that visits web pages without a human user. Search engine bots like Googlebot crawl pages to build their search index. AI bots like GPTBot crawl content for training data. Social media bots fetch pages to generate link previews. Bots typically identify themselves in their user agent string, though this can be spoofed. Regular browsers are controlled by human users and have standard browser UA signatures.
The complexity of user agent strings is a result of decades of browser history. Early websites would check the user agent and only serve advanced features to Netscape (Mozilla). When Internet Explorer appeared, it added Mozilla to its UA string so it would not be blocked. Each subsequent browser followed this pattern, adding tokens from older browsers to avoid compatibility issues. This is why Chrome's UA string includes Mozilla, AppleWebKit, KHTML, and Safari even though it is none of those browsers.