What is My User Agent?
What is a User-Agent?
Your browser sends a User-Agent string with every HTTP request it makes. This string tells the server exactly which browser, version, rendering engine and operating system you are using. Websites and servers use this information to serve compatible content, apply responsive layouts or log visitor statistics.
The string originates from the early days of the web when browsers needed to identify themselves to servers so the server could decide which HTML features were safe to send. Today it also carries information about the device, CPU architecture and installed platform plugins. The format has grown longer and more complex over time and has become something of a historical artefact, since nearly every browser now includes "Mozilla/5.0" at the start regardless of whether it has any connection to Mozilla.
Understanding the Fields
The Browser Engine field tells you the underlying rendering technology. Blink (used by Chrome, Edge and Opera) and WebKit (used by Safari) share common origins; Gecko is used exclusively by Firefox. The engine determines how HTML, CSS and JavaScript are interpreted, which matters for cross-browser compatibility testing.
The Device Model field appears only for mobile devices where the UA string embeds the hardware identifier. On modern iOS devices Safari deliberately omits specific model information to protect privacy. On Android, the model string is provided by the manufacturer and often matches what you see in the device settings.
The Color Depth value represents how many bits are used per pixel in the current display. Most modern screens report 24 or 30 bits. The Do Not Track field reflects whether you have enabled the DNT privacy preference in your browser settings, though websites are not legally required to honour it.
Why Developers Check User-Agents
Web developers use User-Agent information to test how a site behaves across different browsers, operating systems and screen sizes. If a customer reports a display issue, knowing their UA string is often the first step in reproducing the problem. You can copy your full UA string from the bar at the top of this page and paste it into a browser emulation tool or send it directly to a developer for analysis.
The "Parse any UA string" tool at the bottom of the results card lets you paste any UA string and instantly see it decoded. This is useful when reading server logs or support tickets where the raw string is all you have.
User-Agents and Privacy
Major browsers including Firefox and Safari have been reducing the detail in their User-Agent strings to make it harder for websites to fingerprint users based on their exact browser configuration. This process, called UA reduction, means that in the near future many browsers will report a generic string that does not reveal the exact OS version or device model.
Google Chrome is replacing the UA string with a new API called User-Agent Client Hints (UA-CH), which requires websites to explicitly request specific information rather than receiving everything automatically. This gives users more control over what is shared while still allowing legitimate use cases like bug reporting.
Frequently Asked Questions
Can I change my User-Agent?
Yes. Every modern browser has developer tools that let you override the User-Agent string. In Chrome and Edge, open DevTools (F12), click the three-dot menu, go to More Tools then Network Conditions, and uncheck "Use browser default" under User agent. This is useful for testing how a site responds to different browsers or mobile devices.
Why does my User-Agent say "Mozilla/5.0"?
This is a legacy compatibility artefact. In the early browser wars, many web servers only served advanced content to browsers identifying as Mozilla (Netscape). Other browsers began including "Mozilla/5.0" in their strings to avoid being served degraded content, and the practice has stuck ever since. It has no relation to whether you are actually using a Mozilla product.
Can websites block me based on my User-Agent?
Yes. Some websites block known bot User-Agents or restrict access to browsers they do not support. Conversely, some tools spoof browser UAs to bypass these restrictions. This is why UA strings alone are not a reliable form of access control.
Does my User-Agent contain my IP address?
No. The User-Agent string itself contains only browser and device information. Your IP address is sent in a separate part of the HTTP request header. Both pieces of information are visible to the server you connect to.