Hello dontwannagiveone,

Your system details show that you have the "Hide Tab Bar With One Tab " add-on installed .....

Would you disable it and see if that will make a difference  ?

Sorry I guess i rambled on. I meant how do I get rid of the tab bar in version 57 and later. I tried 57 when it came out "one tab" won't work with the "improved Firefox" so I went back to 56.0.2. But I see from past searches I'm the only tab hater and would like to update if only I could get rid of screen wasting annoyiing tab bar Thanks.

You're not the only tab hater. The add-ons site says there are an average of 36 active users of my add-on here:

https://addons.mozilla.org/firefox/addon/i-hate-tabs-sdi-for-firefox/

What it does is watch for new tabs and launch them into their own window. But it doesn't actually hide the one-tab tab bar. For that you would need to use a custom style rule.

Are you already familiar with userChrome.css from making other tweaks to Firefox's toolbar area? If you aren't, when you have 10 minutes to focus on it, here's how it works:

This assumes you do not already have a userChrome.css file. If you do already have a working userChrome.css file, you just need to add the rule under (A) to your file.

(A) Select and copy the following style rule code

/* Squash tab bar to 1px tall and hide the tabs */
#TabsToolbar {
  height: 1px !important;
  min-height: 1px !important;
  max-height: 1px !important;
} 
#TabsToolbar .tabbrowser-tab {
  display: none !important;
}

(B) Generate and download a userChrome.css file

Open the following page and paste the above rules into the editor, replacing the sample rule:

https://www.userchrome.org/download-userchrome-css.html

Then click "Generate CSS File" and save the userChrome.css file to your computer. (See first attached screenshot)

Use the downloads list on the toolbar to open the downloads folder directly to the new userChrome.css file. (See second attached screenshot)

Minimize that Windows Explorer window for later reference.

(C) Create a new chrome folder in your profile folder

The following article has the detailed steps for that (#1, #2, and I recommend #3)

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

I have videos for both Windows and Mac in case the text is not clear.

(D) Move the userChrome.css file you generated in Step B into the chrome folder you created in Step C

The next time you exit Firefox and start it up again, it should discover that file and apply the rules.

I'm not familiar with userchrome.css. I'm trying to digest all this. Thank you

In the View menu is a listing Full Screen F11. This is a toggle on/off.

It expands just the page frame to occupy your entire monitor, and makes all the other menus and tabs go away.