If you want to remove only the small expansion of the bar on new tab (or otherwise change the styling), you can use userChome.css. If you want to remove padding all the time, remove the ":not([open])" parts of the below.
/* based on https://old.reddit.com/comments/fwhlva//fmolndz */
#urlbar[breakout][breakout-extend]:not([open]) {
top: calc((var(--urlbar-toolbar-height) - var(--urlbar-height)) / 2) !important;
left: 0 !important;
width: 100% !important;
}
#urlbar[breakout][breakout-extend]:not([open]) > #urlbar-input-container {
height: var(--urlbar-height) !important;
padding-block: 0px !important;
padding-inline: 0px !important;
}
#urlbar[breakout][breakout-extend][breakout-extend-animate] > #urlbar-background {
animation-name: none !important;
}
#urlbar[breakout][breakout-extend]:not([open]) > #urlbar-background {
box-shadow: none !important;
}
(Source: https://bugzilla.mozilla.org/show_bug.cgi?id=1627861#c3)
If you've not used userChrome.css before, you'll need to enable it.
- First, go to
about:config
, then set toolkit.legacyUserProfileCustomizations.stylesheets
to true
.
- Open
about:support
, then click the "Open Folder" button under "Profile Folder"
- Create a new directory called
chrome
.
- Under the
chrome
directory, create a file called userChrome.css
.
Add the rules specified above and restart Firefox.
If you want a more thoroughly modified address bar, userchrome.org now offers some interactive dropdowns where you can choose exactly how you want the bar to look, along with some screenshots showing you what it will look like.
The megabar pref browser.urlbar.update1
to allow going back to the old version of the bar will be removed entirely as of Firefox 77.
(Source: https://bugzilla.mozilla.org/show_bug.cgi?id=1627969)
toolkit.cosmeticAnimations
out. But no, this setting is obviously not responsible for this behavior.