If I understood correctly, you'd like to reduce the width of tabs, so that you can fit more tabs on the tab bar. The simplest way to do that is to install the Custom Tab Width add-on.

• https://addons.mozilla.org/firefox/addon/custom-tab-width/

You can also right-click any tab and choose Pin Tab. This reduces it to icon size.

• Pinned Tabs - keep favorite websites open and just a click away

Thanks. I was wondering why the tab width changed? I was also wondering if there was a way to put the tab width back to the way they were before without the add-on? I was also wondering if you knew the original tab width? Thanks.

The minimum tab width is set in a style sheet incorporated into one of Firefox's program files. This is very difficult to edit directly because you need to unpack/repack a file (without corrupting it) and repeat that after every update.

Another way to modify that is to create a custom style rule in a userChrome.css file. This post has an example: https://support.mozilla.org/questions/753291?page=2#answer-191051

But I can't think of any recent change. Could any of your other extensions be affecting this?

I don't think any of my extensions could be the cause (I had all of them in the old version (except for the "custom tab width" add-on (which I added)). But I'd like to know what the original tab width could have been? Thanks.

I don't think any of my extensions ...

You don't have to guess, try a little troubleshooting.

There's SafeMode.
Firefox Safe Mode

And there is disabling extensions one at a time to locate the culprit.
Disable or remove addons
You can use that to see if it solves your other thread.
https://support.mozilla.org/en-US/questions/993088

Well, like I said, the only add-on that's new is the "custom tab width" add-on. But I'd like to know what the original tab width could have been? Thanks.

You can reset the browser.tabs.tabMinWidth and browser.tabs.tabMaxWidth prefs on the about:config page that the extension uses.

• http://kb.mozillazine.org/browser.tabs.tabMinWidth
• http://kb.mozillazine.org/browser.tabs.tabMaxWidth

Do you only have an issue with the tab width or also with the tab height?

I was wondering: once I fix the size of the tabs, if I remove the "custom tab-width" add-on, will the tabs go back to being large? I'd like to reduce the number of add-ons I have, so I was just wondering. Thanks.

You would have to use code in userChrome.css instead to keep the tabs at their width if you uninstall the extension.

Add code to the userChrome.css file below the default @namespace line.

• http://kb.mozillazine.org/userChrome.css

@namespace url("http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul"); /* only needed once */

.tabbrowser-tab[fadein]:not([pinned]) { min-width: 100px !important; max-width: 250px !important; }

The customization files userChrome.css (user interface) and userContent.css (websites) are located in the chrome folder in the Firefox profile folder.

• http://kb.mozillazine.org/Editing_configuration