To put borders between tabs you will need to create a file userChrome.css. If you are willing to do that, I will post the code I use. (Remove the blank space in the link below.) https://www.userchrome. org/how-create-userchrome-css.html

@ terry21

Ok, I got that far (I think...). What's next?

Try this (I have made the colour black although I don't use that myself).

.tabbrowser-tab {border-left: 1px solid Black !important;} .tabbrowser-tab[last-visible-tab] {border-right: 1px solid Black !important;}

I use this code in userChrome.css:

 .tab-background:is([multiselected="true"],[selected="true"]) {
   border-top-color: var(--tabs-border-color) !important;
   border-top-style: solid !important;
   border-bottom-color: transparent !important;
 }

 .tab-background:not([selected=true],[multiselected=true]) {
   border: 1px solid rgba(0,0,0,.20) !important;
   border-top-color: transparent !important;
   border-bottom-color: transparent !important;
   background-color: color-mix(in srgb, currentColor 5%, transparent) !important;
 }

Not sure where to put any of that?

Of all the things they felt the need to change, why did it have to be something as simple as letting tabs actually look like tabs? UGH!

It is not that difficult to create userChrome.css if you have never used it.

The first step is to open the "Help -> Troubleshooting Information" page and find the button to access the profile folder.

• https://support.mozilla.org/en-US/kb/use-troubleshooting-information-page-fix-firefox

You can find the button to go to the profile folder under the "Application Basics" section as "Profile Folder -> Open Folder". If you click this button then you open the profile folder in the Windows File Explorer. You need to create a folder with the name chrome in this folder (name is all lowercase). In the chrome folder you need to create a plain text file with the name userChrome.css (name is case sensitive). In this userChrome.css text file you paste the text posted. On Mac you can use the TextEdit utility to create the userChrome.css file as a plain text file.

In Windows saving the file is usually the only time things get more complicated because Windows can silently add a .txt file extension and you end up with a file named userChrome.css.txt. To avoid this you need to make sure to select "All files" in the dialog to save the file in the text editor using "Save File as".

You need to close (Quit/Exit) and restart Firefox when you create or modify the userChrome.css file.

See also: More info about userContent.css and userChrome.css in case you are not familiar: *https://www.userchrome.org/what-is-userchrome-css.html

• https://www.userchrome.org/how-create-userchrome-css.html

In Firefox 69 and later you need to set this pref to true on the about:config page to enable userChrome.css and userContent.css in the chrome folder.

• about:config => toolkit.legacyUserProfileCustomizations.stylesheets = true
• https://www.userchrome.org/firefox-changes-userchrome-css.html