Firefox Styles Snippets (via userChrome.css)

🚧 Work In Progress 🚧

Firefox Styles Snippets (via userChrome.css)

Note: Starting with Firefox 69 you have to enable toolkit.legacyUserProfileCustomizations.stylesheets in about:config.

In 'Profile Directory' (Menu > Help > Troubleshooting Information > Profile Directory) create folder chrome with file userChrome.css.

To find and inspect browser's selectors open Browser Toolbox.

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Completely hide tabs strip

#TabsToolbar {
  display: none;
}

Hide tabs strip only in fullscreen

#TabsToolbar[inFullscreen="true"] {
  display: none;
}

Hide sidebar top-menu

#sidebar-header {
  display: none;
}

Dynamic native tabs

• Set window preface value:
  Sidebery settings > Help > Preface value
  note: in this example: XXX
  note: value can be an "empty" unicode sign
• Set custom css:

#main-window #TabsToolbar {
  height: 29px !important;
  overflow: hidden;
  transition: height .3s .3s !important;
}
#main-window[titlepreface*="XXX"] #TabsToolbar {
  height: 0 !important;
}
#main-window[titlepreface*="XXX"] #tabbrowser-tabs {
  z-index: 0 !important;
}