What Is a User Agent (UA)? How to View and Change It

User Agent (UA for short) is a string used to identify client software, usually a browser. It is sent to a server as part of the browser's request headers, telling the server which browser type, version, and operating system the visitor is using so it can return content in an appropriate format. We rarely see it, but it is always working behind the scenes.

What Is a User Agent Used For?

Websites can use a browser's UA to provide a better experience, for example:

• Display pages correctly: whether you visit from a phone or a computer, the page can be laid out properly;
• Adapt features: some features work only on certain devices, so a site can adjust functionality accordingly;
• Optimize loading: on slower networks, a site may return a simplified page to speed up loading;
• Assist with security detection: help identify whether some unusual traffic comes from automated programs.

Typical User Agent Examples

UA strings vary across devices and operating systems. Here are several common examples (version numbers change over time and are shown only for illustration):

• Chrome (Windows): Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/124.0.0.0 Safari/537.36
• Firefox (Windows): Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:125.0) Gecko/20100101 Firefox/125.0
• Safari (macOS): Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/605.1.15 (KHTML, like Gecko) Version/16.1 Safari/605.1.15
• Edge (Windows): Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/124.0.0.0 Safari/537.36 Edg/124.0.0.0
• Android Chrome: Mozilla/5.0 (Linux; Android 10; K) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/124.0.0.0 Mobile Safari/537.36
• iOS Safari (iPhone): Mozilla/5.0 (iPhone; CPU iPhone OS 16_6 like Mac OS X) AppleWebKit/605.1.15 (KHTML, like Gecko) Version/16.6 Mobile/15E148 Safari/604.1

Components of a User Agent

Breaking down a UA string, it generally contains these parts:

• Mozilla/5.0: inherited from the early Netscape browser era. Almost all modern browsers still use this prefix as a historical convention, and it has no special meaning today;
• (Windows NT 10.0; Win64; x64): operating system information in parentheses, indicating the system type, bitness, and processor architecture;
• AppleWebKit/537.36: indicates the rendering engine used by the browser and its version;
• (KHTML, like Gecko): a rendering-engine compatibility statement;
• Chrome/124.0.0.0: identifies the browser and its version;
• Safari/537.36: many non-Safari browsers also include the word Safari for compatibility with websites that depend on WebKit;
• Mobile: when present, indicates access from a mobile device.

How to View and Change a User Agent

View the UA The easiest way is to visit a browser fingerprint-checking website, which can parse and display the current browser's UA directly. You can also open browser developer tools (usually with F12 or by right-clicking and choosing Inspect), refresh the page in the Network tab, and view the UA string in the request headers of a request.

Common ways to change the UA

• Developer tools: browsers such as Chrome and Firefox can temporarily change the UA through device emulation or network conditions in developer tools, which is useful for development and debugging;
• Browser extensions: extensions such as User-Agent Switcher can quickly switch to preset device UA strings;
• Professional environment management tools: when you need fine-grained control over multiple environments and want the UA to remain consistent with the full browser fingerprint, you can use browser environment management tools such as PurpleMark.

One important reminder when changing the UA If you change only the UA without also adjusting other fingerprint dimensions such as the browser engine, WebGL, and Canvas, a website may still detect an abnormal “UA-environment mismatch.” Professional environment management tools can align other browser fingerprint parameters with the selected UA at the same time, making the environment resemble a real device rather than simply replacing a string.

Why Is Managing UA Important in Multi-Account Scenarios?

In multi-account operations, UA should be handled carefully: the UA of each account should match its corresponding device and system, otherwise the platform may regard the environment as suspicious. At the same time, to reduce accidental association between different accounts, separate accounts will usually have different UA combinations.

For multi-account managers who need strong environment isolation, PurpleMark can provide an independent and complete browser environment for each account and fine-grained control over settings from UA to other fingerprint parameters, making each environment closer to a real device and reducing the risk of accounts being incorrectly linked to one another.

Compliance reminder: all environments and accounts should be used within the rules of the relevant platform. PurpleMark is intended for compliant management of accounts you own, not for bypassing platform restrictions that prohibit certain behavior.

Frequently Asked Questions

What does User Agent mean? A User Agent represents the identity of the client making a network request, usually a browser, and includes information such as device type, operating system, browser type, and version. The server uses this information to return content in an appropriate format.

How can I get my browser's User Agent? Visit a browser fingerprint-checking site to see the UA of your current device, or open browser developer tools, refresh the page in the Network tab, and inspect the UA string in the request headers.

How can I change the User Agent? You can temporarily change the UA in the Network conditions section of browser developer tools, or use extensions such as User-Agent Switcher to quickly switch presets. For environments that require consistency across the full fingerprint, professional tools such as PurpleMark can be used.

What browser is Mozilla/5.0? It does not refer to a specific browser. It is a UA prefix retained by almost all modern browsers, originating from the early internet as a historical convention. The specific identification information that follows it is what actually distinguishes browsers.