Firefox CSS Theme - Dark theme / More compact / Modular / Blur
CSS
1,747
1,164 commits
updated Oct 4, 2026









mod.transparent.bookmarks-bar or mod.transparent.bookmarks-bar.centered in about:config 






In search bar type -> about:config
If it's configured using numbers select number else select boolean and press add -> +
To reset default values
deletethe added preference or set it tofalse(for boolean).To find all added preferences search "mod."
| Preference name | Value | Notes | Preview |
|---|---|---|---|
| mod.number.of.extensions.in.a.row | 1 to 10 | Change number of extensions in one row. Default [4] | |
| mod.extensions.menu.extention-icon.size | 12 to 30 | Change extensions icons size. Default [22] | |
| mod.hide.manage-extensions.button | true | Hide the button that opens all extensions manager inside settings. | |
| mod.disable.extensions-menu.separator | true | Hide sepatator between active and inactive/faded extensions. Only visible when there is at least one faded extension. | |
| mod.hide.faded-extensions.inside.extensions-menu | true | Hide all faded/inactive non interactable extensions from extension menu. Not necessary if they aren't visible by default. |



mod.compact.vertical.tabs in about:config mod.centered.tabs in about:config firefoxcss.disable.tab.preview.panel.fully in about:config mod.disable.scrollbar.in.vertical.tabs in about:config mod.searchBox.focus.outline.enable in about:config firefoxcss.tabs.on.top.enable in about:config. Doesn't work with custom window control buttons for now (linux should work) - Fully padded Window border: Enable mod.main.window.frame.style-1 or mod.main.window.frame.style-2 in about:config
- Default Window border and shadow: Disable mod.disable.browser.border-and-shadow in about:config
mod.search.info.buttons.show.always in about:config 
remove_homepage_shortcut_title_text.css

mod.center.widgets or mod.centered.widgets.hide.title-text in about:config
mod.center.widgets
mod.centered.widgets.hide.title-text
mod.popout.searchbar or mod.popout.searchbar.no-animation in about:config - Combined extra Blur mod.combined.extra.blur, combines: "mod.panel-menu.blur", "mod.searchbar.blur" and "mod.vertical-tabs.expand.blur". Enable in about:config
- Searchbar Blur: Enable mod.searchbar.blur in about:config
- Panel menu Blur: Enable mod.panel-menu.blur in about:config
- Vertical Tabs expand Blur: Enable mod.vertical-tabs.expand.blur in about:config
circular_homepage_shortcuts.css

mod.new-tab.background.blur using Number field in about:config
mod.spill-theme in about:config


mod.card-theme.style.1 or mod.card-theme.style.2 in about:config Will be updated when Firefox fully releases blur

[!IMPORTANT]
1. In
about:configsettoolkit.legacyUserProfileCustomizations.stylesheetsto "True" for your custom themes to work.2. Download latest or your preferred firefox version .zip file.
3. You can find your profile folder by writing
about:supportin URL bar and usingOpen folderinProfile foldersection.4. Put
userChrome.css,userContent.css,ASSETSin chrome folder (createchromefolder inside your main profile folder if it doesnt exist).5. Put any selected extra
.cssmodification files (not folders) fromEXTRA MODSto inside of yourchromefolder.6. File Structure (required files/folders marked with *):
๐
.../your profile/chrome/userChrome.css *๐
.../your profile/chrome/userContent.css *๐
.../your profile/chrome/ASSETS */๐
.../your profile/chrome/[extra modification file].css
[!TIP]
How to Toggle between
LightandDarktheme:
There are two settings to change in firefox (pictures below).
Setting both to auto makes it adapt to your operating system theme.
Setting Theme(2) to
LightorDarkwill force it no matter of Operating System colors.Best to leave Website Appearance(1) settings set to auto and just Change to preferred Theme(2).
- Website appearance (changes new tab and websites colors)
- Theme (changes toolbar and browser text colors, also sets text colors to new tab page).
I use firefox integrated Flexible space for spacing:
Download https://github.com/Alan-Kuan/Firefox-Mod-Blur
Installation Instructions https://github.com/Alan-Kuan/Firefox-Mod-Blur#page_with_curl-installer-script
[!Warning]
Will be updated when firefox fully enables blur. No need to external programs.
Add Rule -> Add Process Rule, type firefox -> add.firefox section. Change Mica to Acrylic for better blur effect.acrylic_micaforeveryone.css from EXTRA THEMES and put it inside Chrome folder (and base files from Installation guide above).firefox section enable Blur Behind so when the window is not active it will still be blurred.Old version files backup: https://github.com/datguypiko/Firefox-old-files-backup
Source for Backdrop filter:
https://www.reddit.com/r/FirefoxCSS/comments/ddi4dc/testing_the_backdropfilter_in_the_url_dropdown/
icons_in_main_menu.css (source)
277 followers ยท starred Jan 2023
59 followers ยท starred Jun 2024
165 followers ยท starred Jul 2025
29 followers ยท starred Jun 2025
Firefox CSS Theme - Dark theme / More compact / Modular / Blur
CSS
1,747
1,164 commits
updated Oct 4, 2026









mod.transparent.bookmarks-bar or mod.transparent.bookmarks-bar.centered in about:config 






In search bar type -> about:config
If it's configured using numbers select number else select boolean and press add -> +
To reset default values
deletethe added preference or set it tofalse(for boolean).To find all added preferences search "mod."
| Preference name | Value | Notes | Preview |
|---|---|---|---|
| mod.number.of.extensions.in.a.row | 1 to 10 | Change number of extensions in one row. Default [4] | |
| mod.extensions.menu.extention-icon.size | 12 to 30 | Change extensions icons size. Default [22] | |
| mod.hide.manage-extensions.button | true | Hide the button that opens all extensions manager inside settings. | |
| mod.disable.extensions-menu.separator | true | Hide sepatator between active and inactive/faded extensions. Only visible when there is at least one faded extension. | |
| mod.hide.faded-extensions.inside.extensions-menu | true | Hide all faded/inactive non interactable extensions from extension menu. Not necessary if they aren't visible by default. |



mod.compact.vertical.tabs in about:config mod.centered.tabs in about:config firefoxcss.disable.tab.preview.panel.fully in about:config mod.disable.scrollbar.in.vertical.tabs in about:config mod.searchBox.focus.outline.enable in about:config firefoxcss.tabs.on.top.enable in about:config. Doesn't work with custom window control buttons for now (linux should work) - Fully padded Window border: Enable mod.main.window.frame.style-1 or mod.main.window.frame.style-2 in about:config
- Default Window border and shadow: Disable mod.disable.browser.border-and-shadow in about:config
mod.search.info.buttons.show.always in about:config 
remove_homepage_shortcut_title_text.css

mod.center.widgets or mod.centered.widgets.hide.title-text in about:config
mod.center.widgets
mod.centered.widgets.hide.title-text
mod.popout.searchbar or mod.popout.searchbar.no-animation in about:config - Combined extra Blur mod.combined.extra.blur, combines: "mod.panel-menu.blur", "mod.searchbar.blur" and "mod.vertical-tabs.expand.blur". Enable in about:config
- Searchbar Blur: Enable mod.searchbar.blur in about:config
- Panel menu Blur: Enable mod.panel-menu.blur in about:config
- Vertical Tabs expand Blur: Enable mod.vertical-tabs.expand.blur in about:config
circular_homepage_shortcuts.css

mod.new-tab.background.blur using Number field in about:config
mod.spill-theme in about:config


mod.card-theme.style.1 or mod.card-theme.style.2 in about:config Will be updated when Firefox fully releases blur

[!IMPORTANT]
1. In
about:configsettoolkit.legacyUserProfileCustomizations.stylesheetsto "True" for your custom themes to work.2. Download latest or your preferred firefox version .zip file.
3. You can find your profile folder by writing
about:supportin URL bar and usingOpen folderinProfile foldersection.4. Put
userChrome.css,userContent.css,ASSETSin chrome folder (createchromefolder inside your main profile folder if it doesnt exist).5. Put any selected extra
.cssmodification files (not folders) fromEXTRA MODSto inside of yourchromefolder.6. File Structure (required files/folders marked with *):
๐
.../your profile/chrome/userChrome.css *๐
.../your profile/chrome/userContent.css *๐
.../your profile/chrome/ASSETS */๐
.../your profile/chrome/[extra modification file].css
[!TIP]
How to Toggle between
LightandDarktheme:
There are two settings to change in firefox (pictures below).
Setting both to auto makes it adapt to your operating system theme.
Setting Theme(2) to
LightorDarkwill force it no matter of Operating System colors.Best to leave Website Appearance(1) settings set to auto and just Change to preferred Theme(2).
- Website appearance (changes new tab and websites colors)
- Theme (changes toolbar and browser text colors, also sets text colors to new tab page).
I use firefox integrated Flexible space for spacing:
Download https://github.com/Alan-Kuan/Firefox-Mod-Blur
Installation Instructions https://github.com/Alan-Kuan/Firefox-Mod-Blur#page_with_curl-installer-script
[!Warning]
Will be updated when firefox fully enables blur. No need to external programs.
Add Rule -> Add Process Rule, type firefox -> add.firefox section. Change Mica to Acrylic for better blur effect.acrylic_micaforeveryone.css from EXTRA THEMES and put it inside Chrome folder (and base files from Installation guide above).firefox section enable Blur Behind so when the window is not active it will still be blurred.Old version files backup: https://github.com/datguypiko/Firefox-old-files-backup
Source for Backdrop filter:
https://www.reddit.com/r/FirefoxCSS/comments/ddi4dc/testing_the_backdropfilter_in_the_url_dropdown/
icons_in_main_menu.css (source)
277 followers ยท starred Jan 2023
59 followers ยท starred Jun 2024
165 followers ยท starred Jul 2025
29 followers ยท starred Jun 2025