What Firefox reveals about your platform on Linux

A website says you are using Linux, but you are not sure what that tells it. Or a support form shows a platform label that does not match the details you expect. On Firefox, that label is a browser-reported hint, not a complete inventory of your computer.

Here is how to inspect the platform string and understand what it can and cannot confirm. The Browser Info and System Info tools can help you compare browser details with information your device makes available.

Check Firefox's reported platform

1. Open Browser Info and review the browser version and engine it reports. This gives you context for how Firefox is identifying itself.
2. To see the exact values directly in Firefox, open the Web Console with Ctrl + Shift + K. Enter navigator.userAgent and press Enter, then repeat with navigator.platform. These are read-only JavaScript values.
3. Look for a platform label such as Linux x86_64 in the result. The user-agent string may also contain X11, an rv value, and a Firefox version.
4. Open System Info and compare its available device details, such as processor, graphics, screen, battery, and network information. It offers a different view from the platform label.

If you want a broader guide to finding platform information across browsers, see How to find your browser's reported platform information.

What the platform details mean

Linux x86_64

This usually indicates a Linux environment and a 64-bit x86 processor architecture. It does not identify the exact Linux distribution, such as Ubuntu or Fedora, or tell you the kernel version. It also cannot confirm the physical processor model by itself. Browser privacy features, compatibility choices, or a user-agent override can make the value less specific or different from the underlying device.

X11

Firefox may include X11 in its user-agent string on Linux. Treat this as a compatibility label, not proof that your current desktop session is using the X11 display server rather than Wayland. Websites should not use that token to diagnose your Linux desktop setup.

The rv and Gecko parts

An rv value is associated with the browser's Gecko engine versioning. The Gecko/20100101 text is a compatibility token, not the date Firefox was installed or updated. A Firefox version near the end of the string is more useful for identifying the browser release.

A value that does not match your system

A platform string is supplied by the browser and can be reduced or changed. A privacy setting, a configuration change, or an extension that changes the user-agent can affect what a site sees. The string should not be treated as proof of a device's operating system or architecture.

Why System Info may show different details

The user-agent describes what Firefox presents to websites for compatibility. System Info reports device information that the browser can access through available browser interfaces. These are separate sources, so their labels and level of detail do not have to match exactly.

For example, System Info can show processor and graphics details when the browser exposes them, while a user-agent platform label may only say Linux and indicate an architecture. Browser access to hardware information is limited. A browser gets only a rounded hint about RAM size, not the exact installed amount, and it cannot verify every hardware or operating-system detail.

Privacy settings and browser protections may reduce some reported details. That does not necessarily mean Firefox is malfunctioning. A website may also parse the user-agent string incorrectly, or rely on an old rule that expects a particular format.

What to check if the label looks wrong

1. Make sure you are checking the intended Firefox profile. A separate profile can have different extensions or privacy settings. Reopen the page in the profile you normally use.
2. Review extensions that modify browser identity. In Firefox, open the menu and choose Add-ons and themes, then review installed extensions. If you use a user-agent switcher, turn it off for the check and reload the page.
3. Compare the two JavaScript values. navigator.platform is a short platform hint, while navigator.userAgent is a longer compatibility string. Differences in wording do not automatically mean the computer is misidentified.
4. Use Linux system information for exact details. If you need the distribution, kernel release, or precise processor model, check those on the computer itself. A website cannot reliably verify them from the user-agent string.

These values describe what Firefox makes available to a page, not a certified record of the computer. Avoid posting a full diagnostic report publicly if it contains details you do not want to share.