You can look at this thread:

• /questions/1384204 Since the last update, the Firefox screen does not fit my system setting(125%)

You can set layout.css.devPixelsPerPx to 1.0 (default is -1) on the about:config page. Adjust its value in 0.1 or 0.05 steps like 1.1 to enlarge or 0.9 to reduce until icons/text looks right. You may need values above 2.0 if you have a high resolution display but make sure not to use values too large or too small.

• modifying layout.css.devPixelsPerPx affects user interface and webpages (global zoom)

Firefox has a Zoom section in Settings to set the default zoom level for webpages.

• Settings -> General -> Language and Appearance -> Zoom

You can open the about:config page via the location/address bar. On the warning page, you can click "Accept the Risk and Continue" to open about:config.

• https://support.mozilla.org/en-US/kb/about-config-editor-firefox

I followed your instructions but didn't change anything.

I changed the setting to 2.0 and nothing changed.

I closed FF and when I restarted nothing had changed - went back to the about:config and the setting had gone back to what it was before I changed it. I can find no way to make it keep what I put in.

As for the main pages - I can change the size/text for the page I am on but it does not change any other page. There has to be a way to change the size/text of ALL PAGES.

Jim brown

You can set a default zoom for all pages in Settings. Scroll down the first page ('General') to the heading Zoom and use the down arrow to select a percentage.

This article may help with the issue of preferences not saving.

https://support.mozilla.org/en-US/kb/how-to-fix-preferences-wont-save