hello, this is a new feature, but work in progress and needing more polish still. at the moment it can be turned off through the browser.urlbar.megabar preference in about:config but this pref might go away eventually when the new design is "finished".

thanks a lot, thanks to philipp I turned off the pop-up urlbar feature, I just hope the compact ui will be still available in the new design.

browser.urlbar.megabar doesn't exist in about:config

try browser.urlbar.update1

I'm had the same issue after updating Firefox Dev edition and setting browser.urlbar.update1 to false didn't fix it.

Took me a while to realise that you have to restart the browser after changing the variable.

set browser.urlbar.update1 to false and then close and reopen FF

Don't have browser.urlbar.update1 either. I have version 62.0 . I fixed the problem by going back to the earlier version.

If you like the new style URL-bar except for the increase in size when active you can add this code to the "userCrome.css" (in the "Chrome" folder in the active Firefox profile). It makes the "popup" URL-bar look like normal (not selected) when active (sets the size == the inactive URL-bar):

/* Make URL-bar look like before by setting the "expanded" URL-bar position/size == the "normal" URL-bar */
#urlbar[breakout-extend]{top:calc((var(--urlbar-toolbar-height) - var(--urlbar-height)) / 2)!important;left:calc((var(--urlbar-toolbar-width) - var(--urlbar-width)) / 2)!important;width:100%!important}
#urlbar[breakout-extend] #urlbar-input-container{height:var(--urlbar-height)!important;padding:0px!important}
.urlbarView{margin:0px!important;width:100%!important}
.urlbarView-row{padding:0px!important}