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The “Sign in to Sync” banner is the account row inside Firefox’s three-bar application menu, not a webpage notification. Firefox does not provide a supported switch specifically for removing that row. You can leave it alone, use Firefox’s profile and Sync controls, or try an old community userChrome.css customization. The commonly cited rule is #PanelUI-fxa-status { display: none !important; }, but it came from a 2016 Mozilla Support forum answer and has not been verified for current Firefox releases.
If your real goal is to stop synchronization, hiding the row is the wrong operation: it changes only the menu’s appearance. Mozilla’s documented method is to sign out of the Firefox account on the device and choose whether locally stored synced data remains.
What the “Sign in to Sync” banner actually is
When Firefox is not signed in to a Mozilla account, the application menu can show a “Sign in to Sync” row. The menu opens from the three horizontal lines in the toolbar. Depending on the Firefox version, the row may be presented as an account, profile, or Sync control rather than using exactly the same wording.
This row is a shortcut to account-related actions. It is not a browser notification, website banner, or indication that Sync is running in the background. Removing it from the menu does not delete an account, disable Firefox Sync, or erase saved data.
Mozilla changes account controls as the interface evolves. Current help describes signing in from the profile icon and managing Sync in Settings, while older releases used different menu labels. That is why a control described in an older screenshot may not appear in the same place today.
Choose the result you actually want
| Goal | What changes | Does Sync remain available? | Officially documented? |
|---|---|---|---|
| Hide the menu row | Only the application-menu interface is altered with custom CSS. | Yes. Account and Sync features still exist elsewhere. | No. The selector is a historical community workaround. |
| Stop Sync on this device | You sign out and decide what happens to locally stored synced data. | No, not while signed out on that device. | Yes. Mozilla documents the sign-out process. |
| Keep the prompt available | No customization is made; Firefox continues showing its normal account control. | Yes. | Yes. This is the default behavior. |
Use the first option only when the visual row is the problem. Use the second when you need to stop synchronization or remove the account connection from that installation.
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Try Firefox’s built-in account controls first
Before editing a profile file, check whether the current interface already gives you the action you need:
- Open Firefox’s application menu with the three-bar button.
- Look for the profile or account icon. The label may say “Sign in,” “Sign in to Sync,” or use account wording that differs from older Firefox versions.
- For Sync settings, open Firefox Settings and select the account or Sync section. The exact section name can vary by release.
- If you want to disconnect the device, use the sign-out command and read Firefox’s prompt about retaining or removing locally stored synced information before confirming.
These controls are supported and survive normal interface updates. They do not, however, offer a documented preference whose sole purpose is to hide the sign-in row while leaving every other account function untouched.
The historical CSS workaround
An archived Mozilla Support forum answer from 2016 identified this selector for the menu row:
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#PanelUI-fxa-status { display: none !important; }The selector targets the element that was then used for the Firefox account status area in the menu panel. It is frequently copied into guides because it is short and specific. It is not an official Mozilla setting, and its compatibility with current Firefox versions is unverified. Firefox can rename, move, or replace the element in a later release, making the rule ineffective or potentially affecting another part of the interface.
Mozilla states that it does not officially support custom style rules in userChrome.css or preference changes made through about:config. Custom rules can stop working after an update and can cause unexpected interface behavior. Treat this procedure as a reversible experiment, not a permanent Firefox feature.
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A profile backup gives you a way back if a typo or incompatible rule affects the browser chrome. Close Firefox before copying or renaming profile files, and keep the original stylesheet unchanged until the customization works.
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- Confirm that you are editing the profile used by the Firefox installation you actually launch. Firefox can have more than one profile.
- Record the current value of
toolkit.legacyUserProfileCustomizations.stylesheetsso you can restore it. - Use a plain-text editor. Do not save the file as rich text, and make sure the filename is exactly
userChrome.css, notuserChrome.css.txt. - Expect the menu wording and internal element names to differ across Firefox versions.
Enable and install userChrome.css
The following procedure reflects Mozilla contributor guidance for enabling legacy profile customizations. The feature is disabled by default.
- In Firefox’s address bar, enter
about:configand press Enter. Accept the warning page if Firefox displays one. - Search for
toolkit.legacyUserProfileCustomizations.stylesheets. - Set the preference to
true. This permits Firefox to load profile-level interface CSS. - Restart Firefox. The preference does not take effect reliably until a restart.
- Find the active profile. Open the Firefox menu, choose Help, then More Troubleshooting Information. In the Troubleshooting Information page, use the profile-folder button. You can also open
about:profilesand identify the profile marked as being used. - Inside that active profile folder, create a directory named
chromeusing lowercase letters. - Inside
chrome, create a plain-text file nameduserChrome.css. - Paste the rule below into the file, then save it:
#PanelUI-fxa-status { display: none !important; }- Close every Firefox window and start Firefox again. A full restart is needed for the browser to read the stylesheet.
Keep the rule on its own line while troubleshooting. Additional customizations can make it harder to determine which selector caused a problem.
Check whether the rule worked
After restarting, open the three-bar menu. If the selector still matches your Firefox build, the account-status row should no longer be displayed. The profile icon, Settings, and Sync data are not necessarily removed; only the targeted menu element is hidden.
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If the row remains, do not assume that the file was ignored for only one reason. Check these possibilities in order:
- Wrong profile: The stylesheet may be in a different profile than the one shown as active in
about:profiles. - Preference not enabled: Verify that
toolkit.legacyUserProfileCustomizations.stylesheetsis still set totrue, then restart again. - Filename or folder error: Confirm the folder is
chromedirectly inside the active profile and the file is exactlyuserChrome.css. - Hidden extension: Some editors or operating systems append
.txt, producing a file Firefox will not load as CSS. - Selector changed: The 2016 rule may simply no longer match the current menu markup. There is no supported guarantee that this selector will be maintained.
- Managed configuration: An organization may control account or customization settings, preventing local changes from behaving as expected.
Do not add random selectors copied from unrelated guides. An incorrect rule can hide controls you still need or create a confusing, partially broken menu.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.How to undo the customization
Reversal is straightforward and should be your first response if the menu looks damaged or Firefox behaves unexpectedly:
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- Open
about:config. - Find
toolkit.legacyUserProfileCustomizations.stylesheetsand set it back tofalse. - Exit Firefox completely.
- In the active profile’s
chromefolder, removeuserChrome.css, or rename it to something such asuserChrome.css.disabledso Firefox no longer loads it. - Restart Firefox and inspect the application menu.
If you made other profile changes, restore the backup only after Firefox is closed. Renaming the file first is useful because it lets you test whether the stylesheet caused the problem without permanently deleting your work.
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Hiding a control is not a privacy or synchronization setting. If you want this device to stop syncing bookmarks, history, passwords, tabs, or other account data, use Firefox’s account controls:
- Open the profile or account control in Firefox’s toolbar or application menu.
- Choose the sign-out option.
- When Firefox asks what to do with locally stored synced data, select the retention or removal choice that matches your requirement.
- Confirm the sign-out, then check the account area to verify that the device is no longer connected.
Read the data-retention prompt carefully. Signing out and removing local data has a different consequence from signing out while retaining information on the device. The menu row may still appear afterward because Firefox can continue to offer a sign-in control even when no account is connected.
Work-managed computers and policy restrictions
On a company, school, or other managed device, Firefox policies can control accounts, Sync, profile preferences, and customization files. An administrator may intentionally require or suppress account features. Do not use about:config or profile CSS to bypass a policy.
If the account row is locked, returns after every restart, or differs between managed and personal installations, ask the administrator which behavior is required. Policy behavior can vary by deployment and Firefox version, and an older community discussion is not a complete current policy reference.
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Quick Recap
Practical decision checklist
- Want only a cleaner three-bar menu? Try the historical CSS rule, understanding that it is unsupported and may be obsolete.
- Want to stop data transfer? Sign out through Firefox’s account controls instead of hiding the row.
- Need a supported approach that will survive updates? Leave the interface unchanged and use the built-in profile and Settings controls.
- Did the customization cause trouble? Disable the legacy stylesheet preference and remove or rename the CSS file.
- Is this a managed installation? Follow the administrator’s policy rather than attempting to override it.
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