Minimal gruvbox skin for firefox.

userChrome.css

#navigator-toolbox { font-family: 'JetBrains Mono' !important; border-bottom: none !important; } #navigator-toolbox #back-button { display: none; } #navigator-toolbox #forward-button { display: none; } #navigator-toolbox toolbarspring { display: none; } #navigator-toolbox .tab-line { display: none; } #navigator-toolbox #urlbar-container {
  padding: 0 !important;
  margin: 0 !important;
}
#navigator-toolbox #urlbar {
  border: none !important;
  border-radius: 0 !important;
  box-shadow: none !important;
}
#navigator-toolbox #PanelUI-button {
  padding: 0 !important;
  margin: 0 !important;
  border: none !important;
}
#navigator-toolbox #nav-bar {
  background: white !important;
  box-shadow: none !important;
}
#navigator-toolbox #pageActionButton {
  display: none;
}
#navigator-toolbox #tracking-protection-icon-container {
  border: none !important;
  padding-right: 0 !important;
}
#fullscr-toggler {
  height: 0 !important;
}
#navigator-toolbox .urlbar-history-dropmarker {
  display: none;
}
#navigator-toolbox #tracking-protection-icon-container {
  display: none !important;
}
#navigator-toolbox #identity-box {
  display: none !important;
}
#navigator-toolbox .tab-close-button, #navigator-toolbox #tabs-newtab-button {
  display: none;
}
#navigator-toolbox .toolbar-items {
  background: #282828 !important;
}
#navigator-toolbox #urlbar {
  background: #1d2021 !important;;
  color: #a89984 !important;
  padding: 0 !important;
  padding-left: 1ch !important;
  font-size: 13px;
  height: 20px;
}
#navigator-toolbox #urlbar-background {
  background: #1d2021 !important;;
  border: none !important;
  margin: 0 !important;
}
#navigator-toolbox #pageActionSeparator {
  display: none;
}
#navigator-toolbox .toolbarbutton-1 {
  background: transparent;
}
#navigator-toolbox #nav-bar-customization-target {
  background: #1d2021 !important;;
}
#navigator-toolbox .toolbarbutton-1 {
  background: pink;
  width: 28px;
}
#navigator-toolbox .toolbarbutton-1 .toolbarbutton-icon {
  display: none;
}
#navigator-toolbox #_d7742d87-e61d-4b78-b8a1-b469842139fa_-browser-action {
  background: #98971a;
    background: #1d2021 !important;
}
#navigator-toolbox #_54e2eb33-18eb-46ad-a4e4-1329c29f6e17_-browser-action {
  background: #d79921;
    background: #1d2021 !important;
}
#navigator-toolbox #downloads-button {
  background: #d79921;
  background: #282828;
    color: #282828;
  background: #1d2021 !important;
}
#navigator-toolbox #PanelUI-button {
  opacity: 1 !important;
    background: #1d2021 !important;
}
#navigator-toolbox #PanelUI-menu-button {
  background: #b16286;
    background: #1d2021 !important;
}
#navigator-toolbox .tabbrowser-tab {
  font-size: 12px
}
#navigator-toolbox .tabbrowser-tab .tab-icon-image {
  display: none;
}
#navigator-toolbox .tabbrowser-tab[selected='true'] .tab-icon-image {
  display: none !important;
  height: 16px !important;
  width: 16px;
}
#navigator-toolbox .tab-background {
  background: #282828 !important;
  border: none !important;
  box-shadow: none!important;
  border: none !important;
}
#navigator-toolbox .tabbrowser-tab .tab-label {
  color: #a89984 !important;
}
#navigator-toolbox .tab-background[selected="true"] {
  background: #a89984 !important;
}
#navigator-toolbox .tabbrowser-tab[selected="true"] .tab-label {
    color: #1d2021 !important;;
}
#navigator-toolbox .tabbrowser-tab::after {
  display: none !important;
}

#navigator-toolbox #urlbar-zoom-button {
  border: none !important;
}

/* hide tab if only one tab */
#tabbrowser-tabs, #tabbrowser-tabs > .tabbrowser-arrowscrollbox {
	min-height: 0 !important;
}
#tabbrowser-tabs .tabbrowser-tab[first-visible-tab="true"][last-visible-tab="true"]{
  visibility: collapse !important;
}