I am autistic and have ADHD and agree - the lack of visible delineation between tabs is a nightmare for me.

I agree with Anne and am glad to see her response. I think her take, and mine, are right on the money.

I really, really dislike the new format. I am far-sighted due to normal aging and content is much harder to read.

It seems Firefox has reduced the contrasts and thus the readability. The font is lighter and seems smaller, and the items in menu lists are spaced farther apart e.g. Bookmarks.

Spreading illegible content over a larger area makes it harder, not easier, to find what I'm looking for.

If you prefer the colors of the "Default" theme from Firefox 57-88, someone created an add-on theme that emulates it. You can give it a try here:

https://addons.mozilla.org/firefox/addon/photon-colors/

But that won't restore vertical divisions between the background/inactive tabs. There isn't a convenient way to do that.

I can give you a quick short-term workaround, but a more durable solution will require more work.

Temporary Fix

For testing purposes, there is a preference to switch the tab bar and address bar between new style and old style. This is not expected to continue in Firefox 90, but maybe you want to use it for now.

(1) In a new tab, type or paste about:config in the address bar and press Enter/Return. Click the button accepting the risk.

(2) In the search box in the page, type or paste browser.proton.enabled and pause while the list is filtered

(3) Double-click the preference to switch between true (new style) and false (old style)

Longer Term Community Workaround

This involves setting up a userChrome.css file. I have a rules builder that will get more features throughout the month. By the time the above preference is removed, it should be mature. If you want to take a sneak peek now:

• https://www.userchrome.org/firefox-89-styling-proton-ui.html#tabstyler
• https://www.userchrome.org/how-create-userchrome-css.html