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On Firefox 157 for desktop, you can make the redesigned browser feel more familiar by choosing Compact density, restoring toolbar items, and applying a theme. Those supported changes do not recreate Firefox 156 exactly. Mozilla documents a separate sidebar rollback, while a broader rollback preference reported by forum users is an unsupported, uncertain workaround.
Start with the supported appearance controls
Firefox 157.0 reached Release users on September 29, 2026, with a visual refresh to toolbars, the sidebar, menus, and other features. The steps below apply to Firefox desktop; labels and available options can vary by operating system and later releases. Mozilla’s Firefox 157 release notes describe the redesign and the changes available to users.
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Make tabs and toolbars more compact
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Open Firefox Settings and select Appearance.
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Under Window density, choose Compact. Mozilla says this reduces the space used by toolbars and controls, leaving more room for web content.
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Compact density was added in Firefox 157. Older instructions that use about:config to expose Compact mode are for earlier versions and are not needed for this setting in Firefox 157.
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Put familiar controls and bars back
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Open the Firefox menu, then choose More Tools > Customize Toolbar.
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Drag toolbar items to the positions you prefer. Use the available toolbar options to show the Title Bar, Menu bar, or Bookmarks toolbar.
Linux menu options can vary with the desktop environment. Avoid choosing Restore Defaults unless you want a broader reset: Mozilla warns that it resets the default theme and, when vertical tabs are enabled, switches them to horizontal tabs. See Mozilla’s toolbar customization guide.
Use a theme to approximate the older colors
A Firefox theme can change the toolbar color and background imagery, but it does not restore the old layout, tab geometry, or every control behavior. Mozilla says Firefox supports lightweight background themes; complete themes are no longer supported.
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Open Extensions and themes, then select Themes.
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Choose and enable a theme. You can also browse themes through Mozilla’s theme guide.
Mozilla Add-ons Community said on September 29, 2026, that a Firefox Proton theme was being featured for people seeking the previous visual treatment. Treat it as a color and background approximation, not a complete rollback. Nova also changes where some theme properties appear, although themes continue to load and most color and image properties work, according to the Mozilla Add-ons Community’s Nova theme notes.
Choose how much of the redesign to undo
| Option | What it changes | Support and tradeoff |
|---|---|---|
| Compact density and toolbar customization | Spacing, toolbar arrangement, and visible bars | Built-in Firefox controls; does not recreate the old interface. |
| Theme | Toolbar color and background imagery | Documented theme feature; does not restore layout or tab shape. |
sidebar.revamp=false |
Restores the previous sidebar version | Documented in Firefox 157 release notes; disables vertical tabs. Mozilla says the preference remains available until the end of 2027. |
browser.nova.enabled=false |
Forum users report that it reverts the broader Nova interface | Community-reported, not documented as the official rollback in release notes. No availability end date is established. |
userChrome.css |
Can style individual browser interface details | Advanced and unsupported; rules can stop working when Firefox changes. |
Restore the previous sidebar, with its tradeoff
Firefox 157’s release notes document setting sidebar.revamp to false in about:config to restore the previous sidebar version. This also disables vertical tabs, so use it only if that tradeoff suits your workflow. Mozilla states that this preference will remain available until the end of 2027; it is a sidebar-specific rollback, not a promise to restore all of Firefox 156.
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A user in the Mozilla Support forum discussion about reverting Firefox 157 reported that setting browser.nova.enabled to false brought back the older look on their installation. That is an individual report, not a documented or guaranteed rollback. The forum discussion includes moderator caution, and there is no confirmed end date for this preference.
If you still choose to try an advanced preference, first note its existing value and understand how to restore it. Mozilla warns that changing settings in about:config can cause unexpected behavior or break Firefox, and updates can affect preferences. The documented sidebar.revamp setting and the forum-reported browser.nova.enabled setting are not interchangeable. Mozilla’s advanced customization guidance explains the risks of direct preference changes.
Use custom CSS only if you can maintain it
Advanced users can use userChrome.css to style parts of the browser interface, but Mozilla does not officially support custom style rules. Interface changes can alter the elements those rules target, so CSS may need repair or may stop working after an update.
To undo this customization, set toolkit.legacyUserProfileCustomizations.stylesheets to false in about:config, then remove or rename userChrome.css in the Firefox profile’s chrome folder. Mozilla documents the process in its Firefox CSS customization guide. A Firefox Refresh is not the first recovery choice because it can remove add-ons and other customizations.
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