Firefox Quantum (Target v59.0.1) Super Slim User Interface

userChrome.css

@namespace url("http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul");

/* 1. Navigate to about:support in Firefox and click the button under the Profile Folder heading.
   2. Enter the folder ending in .default (probably something like m61ofslb.default).
   3. Create a folder named chrome if it doesn't exist already.
   4. Drop this file into that folder and restart your Firefox browser.
	
   Designed for Firefox Quantum on Mac OSX and may require modification to work on other operating systems. */

.tab-close-button
	{
	height:15px !important;
	}
	
#TabsToolbar 
	{ 
	height: 10px !important; 
	}

:root
	{
	--tab-min-height: 22px !important;
	--toolbarbutton-border-radius: 2px !important;
	}
	
toolbar .toolbarbutton-1 > .toolbarbutton-icon 
	{
	width: calc(2 * var(--toolbarbutton-inner-padding) + 8px) !important;
	}

.urlbar-input-box 
	{
	font-size: 12px !important;
	}

#nav-bar-customization-target
	{
	height: 28px !important;
	}
	
#urlbar
	{
	min-height: 22px !important;
	}
	
#identity-box 
	{
	padding-inline-start: 2px !important;
	padding-inline-end: 0px !important;
	margin-inline-end: 2px !important;
	}
   
:root:not([uidensity="compact"]) #back-button > .toolbarbutton-icon 
	{
	padding: 3px !important;
	}
	
.toolbarbutton-icon
	{
	padding:4px !important;
	}
	
.titlebar-placeholder[type="pre-tabs"] 
	{
	width: 12px !important;
	}

.tab-throbber, .tab-throbber-fallback, .tab-icon-image, .tab-sharing-icon-overlay 
	{
	height: 13px !important;
	width: 13px !important;
	}