Multi Row Tabs in Firefox Quantum

[OBSOLETE stopped working with firefox 71]

The Tab Mix Plus addon stopped working with v57 :-(

  1. Open about:config and set toolkit.legacyUserProfileCustomizations.stylesheets to true.
  2. Open a new tab on about:support
  3. Click the button next to “Profile Folder”
  4. Go to the “chrome” directory at the profile folder, or create it if it doesn’t exist.
  5. Create a file named “userChrome.css” (if it doesn’t exist) and open it in a text editor.
  6. Copy the css code from
    (copy of the css is at the bottom of this post)
  7. Paste it into userChrome.css and save.
  8. Restart Firefox

Update for v58: Changed .tabbrowser-tabs to #tabbrowser-tabs.

Update for v65: Removed #titlebar related stuff


.tabbrowser-tab:not([pinned]) {
.tabbrowser-tab,.tab-background {
.tab-stack {
    width: 100%;
#tabbrowser-tabs .scrollbox-innerbox {
    display: flex;
    flex-wrap: wrap;
#tabbrowser-tabs .arrowscrollbox-scrollbox {
    overflow: visible;
    display: block;
#tabbrowser-tabs .scrollbutton-up,#tabbrowser-tabs .scrollbutton-down,#alltabs-button,.tabbrowser-tab:not([fadein]){
    display: none;
#main-window[sizemode="maximized"] #TabsToolbar{
    height:var(--tab-min-height) !important;
    margin-bottom:calc(var(--tab-min-height)*-1) !important;
#main-window[sizemode="maximized"] #titlebar{
    margin-bottom:calc(6px + var(--tab-min-height)*-1) !important;
    margin-bottom:0 !important;
#titlebar:active #titlebar-content{
    margin-bottom:var(--tab-min-height) !important;

Based on instructions here.