Latest Firefox User Agent Strings: Windows, macOS, Linux, Android & iOS

Latest Firefox Desktop User Agent

The current Firefox desktop user agent string (Firefox 152, Windows 10/11) — copy it directly:

Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:152.0) Gecko/20100101 Firefox/152.0

Firefox 152.0 reached the release channel on June 16, 2026. The user agent only ever exposes the major version — point releases like 152.0.6 still send Firefox/152.0. Firefox 153 is scheduled for July 21, 2026, after which the version tokens bump to 153.0. You can always confirm the current release on our latest Firefox version page.

Latest Firefox User Agent Strings by Platform

Every string below reflects Firefox 152, the current stable release. Note that several tokens are deliberately frozen and don’t describe your real system — see the format breakdown further down.

Windows 10 / Windows 11

Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:152.0) Gecko/20100101 Firefox/152.0

Windows 11 sends the same string — Windows NT 10.0 is reported on both. See more on our Windows user agents page.

macOS

Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:152.0) Gecko/20100101 Firefox/152.0

The macOS version is capped at 10.15 since Firefox 87, and Apple Silicon Macs still report Intel — both anti-fingerprinting measures. Compare with other browsers on our macOS user agents page.

Linux

Mozilla/5.0 (X11; Linux x86_64; rv:152.0) Gecko/20100101 Firefox/152.0

Ubuntu builds (including the snap) add a distro token:

Mozilla/5.0 (X11; Ubuntu; Linux x86_64; rv:152.0) Gecko/20100101 Firefox/152.0

X11 is reported even under Wayland, and since Firefox 127 even 32-bit builds report x86_64.

Android (Firefox & Firefox Focus)

Mozilla/5.0 (Android 10; Mobile; rv:152.0) Gecko/152.0 Firefox/152.0

The OS token is frozen at Android 10 since Firefox for Android 122 regardless of your real Android version, and on Android the Gecko token carries the Firefox version (Gecko/152.0) instead of the desktop’s fixed Gecko/20100101. Tablets send Tablet; in place of Mobile;. Firefox Focus on Android is GeckoView-based and sends the same string as Firefox for Android, with no separate Focus token. More on our Android user agents page.

iOS (Firefox & Firefox Focus)

Mozilla/5.0 (iPhone; CPU iPhone OS 15_7_7 like Mac OS X) AppleWebKit/605.1.15 (KHTML, like Gecko) FxiOS/152.0 Mobile/15E148 Safari/605.1.15

Firefox on iOS must use Apple’s WebKit engine, so its user agent looks like Safari’s with an FxiOS/152.0 token identifying Firefox. Unlike the frozen desktop tokens, the iPhone OS version here mirrors the device’s actual iOS version (a current iPhone shows e.g. 26_5), and iPads send iPad; CPU OS … instead. Firefox Focus on iOS uses the same format with Focus’s own version number after FxiOS/. Compare with our iOS user agents and Safari user agents pages.

Firefox Extended Support Release (ESR) User Agents

Firefox ESR is the Extended Support Release: a stable branch that receives only security and stability updates for about a year, used by enterprises, schools, and Linux distributions that can’t absorb a feature update every four weeks. QA teams need ESR user agents because a large share of corporate traffic runs these versions, not the latest release. Two ESR lines are currently maintained — ESR 140 (current: 140.12.0, supported until September 2026) and the legacy ESR 115 (current: 115.37.0, kept alive for Windows 7/8/8.1 and older macOS until March 2027):

Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:140.0) Gecko/20100101 Firefox/140.0

ESR 115 on Windows 7 identifies the older OS (Windows NT 6.1):

Mozilla/5.0 (Windows NT 6.1; Win64; x64; rv:115.0) Gecko/20100101 Firefox/115.0

ESR strings are indistinguishable from a regular release of the same number — point releases (140.12.0) are never exposed, so ESR 140 simply sends Firefox/140.0. The next ESR base will be Firefox 153.

Firefox User Agent Format Explained

Every Firefox desktop user agent follows the same five-part pattern:

Mozilla/5.0 (platform; rv:geckoversion) Gecko/geckotrail Firefox/firefoxversion

• Mozilla/5.0: A legacy identifier kept for compatibility — every modern browser sends it, dating back to Netscape Navigator.
• (Windows NT 10.0; Win64; x64): The platform token — operating system and architecture. Several values are deliberately frozen (see below).
• rv:152.0: The Gecko release version, which matches the Firefox major version.
• Gecko/20100101: The rendering engine token. On desktop it’s the fixed string 20100101 — a compatibility token, not a real date. On Android it carries the version instead (Gecko/152.0).
• Firefox/152.0: The browser and its major version — never point releases.

Why so many frozen tokens? Fingerprinting reduction. Firefox reports Windows NT 10.0 on Windows 11, caps macOS at 10.15, freezes Android at 10, reports Apple Silicon as Intel and 32-bit Linux as x86_64 — every real detail removed from the string makes users harder to single out.

How to Override and Reset the Firefox User Agent via about:config

Override the user agent

• Type about:config in the address bar, press Enter, and click Accept the Risk and Continue.
• Search for general.useragent.override — this preference doesn’t exist in a default profile; you’ll create it.
• Select the String type and click the + button.
• Paste your replacement user agent string as the value and press Enter to save — the override applies to all requests from then on, no restart needed.
• Caveat: if privacy.resistFingerprinting is enabled, Firefox ignores the override and sends its generic spoofed user agent instead.

Reset to the default user agent

• Open about:config again and search for general.useragent.override.
• Click the trash-can (Delete) button next to the preference. Because the preference is user-created, deleting it removes the override entirely and restores Firefox’s default user agent immediately.

For quick device-specific checks you don’t need about:config: Firefox’s Responsive Design Mode (Ctrl+Shift+M in DevTools) can emulate device viewports with matching user agents, and extensions like User-Agent Switcher offer per-site switching. To generate test strings in bulk, try our free user agent generator. And remember an override only changes the string — it doesn’t change how Gecko renders, so for real cross-browser results you still need to test on real Firefox versions.

Can Websites Track You Through Your User Agent?

Yes — the user agent is a classic browser fingerprinting signal: combined with screen size, fonts, and other attributes, the OS/browser/version combination narrows visitors into small, identifiable buckets. That’s exactly why Firefox freezes so many tokens, and why privacy.resistFingerprinting goes further by reporting a generic, ESR-rounded user agent for everyone who enables it. Also worth knowing: Firefox does not implement User-Agent Client Hints (the Sec-CH-UA headers and navigator.userAgentData API that Chromium browsers use) — sites must parse the classic User-Agent header for Firefox visitors, unlike the hint-based flow described on our Chrome user agents and Edge user agents pages.

How to Check Your Firefox User Agent

Via Firefox Browser:

• Open Firefox and go to about:support in the address bar.
• Look under the User Agent section to view your current string.

Using JavaScript:

• Open Developer Tools (F12) in Firefox.
• Go to the Console tab and type the following:

navigator.userAgent;

Using Online Tools:

Use our free What Is My User Agent tool to instantly see your current string, or paste any string into the user agent parser to decode its browser, engine, and OS tokens.

What is my User Agent?

Frequently Asked Questions About Firefox User Agents

What is the latest Firefox user agent string?

As of July 17, 2026, the latest Firefox desktop user agent is Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:152.0) Gecko/20100101 Firefox/152.0, reflecting Firefox 152 (released June 16, 2026). The user agent only ever exposes the major version — point releases like 152.0.6 still send Firefox/152.0. Firefox 153 ships on July 21, 2026, which will bump the version tokens to 153.0.

How do I reset the default user agent on Firefox?

Open about:config in the Firefox address bar, accept the warning, and search for general.useragent.override. Click the trash-can (Delete) button next to the preference to remove it — since this preference doesn't exist in a default profile, deleting it fully restores Firefox's default user agent. If you only modified an existing preference, you can also right-click it and choose Reset.

Can my user agent be used to track me?

Yes — the user agent is a classic browser-fingerprinting signal, since the combination of browser version, OS, and platform narrows users into small buckets. Firefox limits this by freezing tokens: it always reports Windows NT 10.0 (even on Windows 11), caps macOS at 10.15, reports Android 10 regardless of the real version, and exposes only the major Firefox version. For stronger protection, the privacy.resistFingerprinting preference makes Firefox report a generic, ESR-rounded user agent so individual users blend into one crowd.

What is Firefox's default browser agent?

The phrase has two meanings. Firefox's default user agent is the string it sends with every request — for example Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:152.0) Gecko/20100101 Firefox/152.0 on Windows. Separately, the 'Firefox Default Browser Agent' is a small scheduled task Firefox installs on Windows that periodically checks whether Firefox is set as the system default browser; it can be disabled via the default-browser-agent.enabled policy and is unrelated to the user agent string.