The normal way is by using these two ''browser.tabs.tab'' prefs to control the minimum tab width (50 or higher) and the clip-width that controls when to hide the close button (make both the same). *browser.tabs.tabMinWidth = 50 *browser.tabs.tabClipWidth = 50 Otherwise you need to use code in userChrome.css to get more control, I use code to hide the close button and make it visible after a short delay to prevent accidentally closing a small tab by clicking it. *[/questions/1403517] userChrome.css is not being applied (fixed for 113) *https://www.userchrome.org/what-is-userchrome-css.html