Need help with Firefox Update 63 (sidebar spacing)

Update 63 just installed, and it has broken a key customization I’d like to get back. I tried going to the mozilla forums but I either couldn’t find them or couldn’t make heads or tails out of them.

Sidebar vertical spacing

My sidebar is always open. For years and years I’ve had the sidebar spacing set to the minimum (1px) to fit as many bookmarks on the screen as possible without scrolling, but this new update has changed it back to the default spacing. Now instead of 39 bookmarks being visible on the screen without scrolling, only 29 fit. This is a significant loss of functionality, and I’d like to get back to my 1px spacing. Can anyone help?

Note that my userChrome.css file is right where it’s always been, and while it stills correctly suppresses the sidebar search box, it’s not doing anything for the vertical spacing.

@namespace url(;  /* only needed once */

.sidebar-placesTreechildren::-moz-tree-row {
  height: 1px !important;

#sidebar-header, #search-box { display:none!important; }

bookmarks-view treechildren {background-color:#AAA99!important}

Anyone have any ideas?

I have a partial fix, but this adds a new annoyance:

@namespace url(;  /* only needed once */
/* negative amounts, when allowed, can pack lines close */
#bookmarks-view treechildren::-moz-tree-row {
  margin-top: -3px !important;
  margin-bottom: -3px !important;

#sidebar-header, #search-box { display:none!important; }

This technically works in that my sidebar now looks the same as it did before the update. Unfortunately, it no longer redraws rows correctly, so every time I move the mouse in the sidebar, it leaves ugly grey lines in between the bookmarks.

Obviously the negative margins are messing with the drawing function. For now I’ll change the highlight color from #AAA99 to White, but the bottoms of hanging letters (g, y, etc…) get cut off by the faulty redrawing when I move the mouse around. Plus I no longer have any highlight at all, which is a bummer.

Is there any way to fix this? Should I start looking into just switching to chrome? I’m so sick of Firefox breaking my interface every friggin’ update.

I have no advice on userChrome other than to tell you to ask here.

That said, I do know that Chrome, since it doesn’t have a built in sidebar, has a lot of bookmark sidebar extensions. Firefox doesn’t seem to have any, but you might be able to get those extensions to run in Firefox using the Chrome Store Foxified addon.

Chrome’s UI is much less customizable than Firefox’s. So if you’re into UserChrome tweaks, you may not like it. I would instead recommend Firefox 60 ESR if nothing else is sufficient, and you just want to keep the old interface. It will continue working until Firefox 70 works out, with only security updates.

That said, there’s nothing wrong with downloading Chrome, adding the extensions, and seeing if it’s for you. I use it now.

I had the same problem. I think Firefox added or changed the min-height property in treechildren::-moz-tree-row
Here’s what I’m now using. Adjust the 1.3em, 1.5em, and 9pt to taste.

@namespace url(""); /* set default namespace to XUL */
.sidebar-placesTree treechildren::-moz-tree-row, .placesTree treechildren::-moz-tree-row {
	min-height: 1.3em !important;  /* FF63 appears to have changed this */
	height: 1.5em !important;      /* Active if > min height */
        border-width: 0 !important;    /* not sure if this is needed*/
 #bookmarks-view {
	 font-size: 9pt !important; /*no vertical sizing change, but can change overall appearance*/

Awesome, that totally works! All fixed now, thanks much, you rock!

For the record, I just pasted your code in and it perfectly matched what I wanted, no changes to 1.3em, 1.5em, or 9pt needed.

EDIT: I think problem is that 63 introduced “themed sidebars,” which of course I have no idea how to manipulate. But I assume that adding the ability to theme them involved breaking some old-style customizations via userChrome.css. My original css fix in the OP was from several years ago.