If you only want the Sign in to Sync row out of Firefox’s three-bar menu, the selector most often cited is #PanelUI-fxa-status { display: none !important; }. It comes from a 2016 Mozilla Support forum answer, not current official documentation, and its compatibility with present Firefox releases is unverified. The method requires enabling the unsupported userChrome.css customization system. If your goal is to stop synchronization rather than tidy the menu, use Firefox’s account controls to sign out instead.
First decide whether you want a hidden control or no syncing
The menu row and the Sync service are separate things. A CSS rule can hide a piece of Firefox’s application interface while leaving your account, devices and synchronization capability unchanged. You could still manage Sync from Firefox’s profile controls or Settings; the menu item would simply no longer be visible.
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Stopping Sync is a different operation. Mozilla’s documented device procedure is to sign out of the Firefox account and choose whether locally synced data should remain on that device. That action affects the account connection and local data choice; hiding a row does neither.
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|---|---|---|---|
| Remove the menu row | The application-menu interface only; Sync remains available elsewhere | The selector is an old community workaround and may become obsolete | Optional userChrome.css customization |
| Stop syncing this device | The device’s Firefox-account connection and your choice about local synced data | Documented by Mozilla | Profile/account controls, then sign out |
Do not use the CSS method as a privacy or security control. It changes what you see, not what Firefox synchronizes.
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Check Firefox’s built-in controls before editing files
Firefox changes menu labels and account placement between releases. In current help, Mozilla describes signing in from the profile icon and managing Sync in Settings. Open the application menu with the three-bar button and look for the profile or account area; on some versions the wording is Sign in to Sync, while other versions may show an account name, profile icon or a different prompt.
To manage or disable Sync normally
- Open Firefox’s application menu.
- Select the profile or account control. If the menu does not expose it, open Settings and use the Firefox account/Sync section.
- To disconnect this installation, choose the sign-out command and read Firefox’s prompt about retaining or removing locally synced data.
- Confirm only after checking which local information you want to keep. This is the documented way to stop synchronization; it does not require custom CSS.
If the account row is missing, renamed or located elsewhere, note your Firefox version and whether the browser is managed by an organization. Interface variation alone is not evidence that Sync is disabled.
What the historical CSS workaround does—and does not promise
The commonly cited rule is:
#PanelUI-fxa-status { display: none !important; }The #PanelUI-fxa-status ID was used for the account-status row in the menu panel referenced by a 2016 archived Mozilla Support forum answer. The answer is community guidance from that time, not a current Mozilla configuration guarantee. Firefox’s internal markup can change without notice, so the ID may no longer match anything, may hide a different element, or may produce no visible result in a newer release.
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Mozilla explicitly says it does not officially support custom style rules in userChrome.css or userContent.css, nor preference changes made through about:config. Custom rules can stop working after an update and can cause unexpected interface behavior. Treat this as a reversible experiment for a personal profile, not as a supported feature or a permanent fix.
Prepare a reversible profile customization
Firefox loads userChrome.css only when the legacy customization preference is enabled and the file is placed in the active profile’s chrome directory. A profile is a separate data folder; editing a different profile will have no effect.
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1. Identify the active profile
- In Firefox, open the menu and choose Help, then More Troubleshooting Information. You can also type
about:profilesin the address bar. - Find the profile marked as the one in use. Use its Open Folder or equivalent button to open the profile directory in your operating system’s file manager.
- Close Firefox before creating or editing the stylesheet. Keeping the browser closed prevents a running process from overwriting or masking your changes.
Profile folders can be hidden by the operating system. Use the profile page’s open-folder command rather than guessing a path. If you have several profiles, record the folder name so you can reverse the change in the same place later.
2. Enable legacy stylesheet loading
- Start Firefox and enter
about:config. - Accept the warning page only if you understand that preference changes are unsupported and can affect the browser.
- Search for
toolkit.legacyUserProfileCustomizations.stylesheets. - Set the Boolean value to
true. - Quit and restart Firefox. The restart is required before Firefox will load the profile stylesheet.
This preference is disabled by default in Firefox. Enabling it does not install a theme or extension; it tells Firefox to read CSS files from the profile.
3. Create the folder and stylesheet
- Return to the active profile directory identified earlier.
- Create a new folder named exactly
chrome, using lowercase letters. - Inside that folder, create a plain-text file named exactly
userChrome.css. Make sure your operating system has not silently appended.txt; the complete filename must end in.css. - Open the file in a plain-text editor and add the selector on its own line:
#PanelUI-fxa-status { display: none !important; }- Save the file as plain text, close the editor and restart Firefox again.
- Open the three-bar menu and check whether the account row is hidden.
Keep a backup copy of the original profile before changing files. At minimum, preserve a copy of the untouched userChrome.css (if one already exists) and note the preference’s original value. A backup lets you recover from a malformed rule or an interface that becomes difficult to use.
If nothing changes, troubleshoot in this order
Confirm the file is in the profile Firefox actually uses
The most common harmless failure is editing the wrong profile. Reopen about:profiles, use the profile marked as in use, and verify that the folder contains chrome/userChrome.css. A file in Downloads, the Firefox installation directory or another profile will not be read.
Check exact names and extensions
The folder must be chrome; the file must be userChrome.css. Case normally matters less on some operating systems, but exact spelling avoids cross-platform problems. Turn on visible file extensions in the file manager and remove an accidental .txt suffix.
Verify the preference and restart
Search for the complete preference name, confirm it is Boolean true, then fully quit and reopen Firefox. Closing only a window may leave Firefox running in the background on some systems; use the normal quit command and start it again.
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If the file loads but the row remains, the historical ID may no longer exist in your Firefox build. There is no supported guarantee that a replacement selector will be stable, and this article does not claim that the 2016 rule works in current releases. Do not hide unrelated controls by guessing at new IDs. Remove the rule if it produces side effects.
Recover from a broken interface
Start by closing Firefox and temporarily rename userChrome.css to something such as userChrome.css.disabled. Reopen Firefox. If the interface is still abnormal, set toolkit.legacyUserProfileCustomizations.stylesheets to false in about:config and restart. These steps disable custom stylesheet loading without deleting your profile data.
How to undo the customization completely
- Open
about:configand settoolkit.legacyUserProfileCustomizations.stylesheetstofalse. - Quit Firefox.
- In the active profile’s
chromefolder, removeuserChrome.cssor rename it so it no longer has the.cssextension. - Restart Firefox and confirm that the normal menu interface has returned.
Renaming rather than deleting preserves the rule if you need to inspect it later. If you had an earlier stylesheet, restore that backup instead of leaving a blank replacement.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.Hiding the row does not turn Sync off
After applying the rule, Firefox can still synchronize data if the browser remains signed in. Bookmarks, history, passwords, open tabs or other categories selected in the account settings are governed by Sync settings, not by the menu row’s visibility.
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If your purpose is to stop data transfer from one computer, use the profile/account control or Settings and sign out. Read the confirmation dialog carefully: Firefox asks whether to retain or remove locally synced information. The correct choice depends on whether you need that data offline. Hiding the control can make later account management less obvious, so record how to reach Settings before applying it.
Work-managed computers need a different approach
On an employer-, school- or otherwise organization-managed installation, Firefox policies can control account features and preferences. A missing control may be intentional. Do not change policy-related preferences or use CSS to bypass an administrator’s requirement. Ask the administrator which account and Sync behavior is permitted.
Policy behavior and menu presentation vary by Firefox version and deployment configuration. An older community discussion is not an exhaustive or current policy reference, so treat it only as a reason to check with the person who manages the device.
Practical decision checklist
- You only dislike the menu row: Try the historical rule only on a personal profile, after backing up, and accept that it may fail after an update.
- You want Sync stopped: Sign out through the profile/account controls and make an explicit local-data choice.
- You need a supported solution: Leave the interface unchanged and use Firefox’s built-in account and Settings controls.
- The browser is managed: Contact the administrator rather than modifying policy or attempting to conceal the control.
- The browser breaks after editing: Disable the preference, rename the stylesheet and restart before investigating further.
The safest expectation is limited: the CSS can remove a visual row if that old selector still maps to the account-status element in your build. It cannot disable Sync, guarantee compatibility across Firefox updates or replace Mozilla’s supported account controls.
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