You can rename (or delete) the content-prefs.sqlite file in the Firefox profile folder to reset the page zoom for all websites.

Type about:support<enter> in the address bar.

Under the page logo on the left side, you will see Application Basics. Under this find Profile Folder. To its right press the button Show Folder. This will open your file browser to the current Firefox profile. Now Close Firefox.

Locate the above file. Then rename or delete it. Restart Firefox.

Hi Parva, Firefox stores zoom levels on a "per site" basis. If you want to set 110% or 120% as your new default zoom level for all sites, you can use an add-on for that. I haven't researched them for a while, but as an example, this one can do it: https://addons.mozilla.org/firefox/addon/zoom-page-we/

In their screenshot, in the "Zoom Levels" box, it's the setting labeled "Default Level":

In case you use "Clear history when Firefox closes" or otherwise clear history.

• do not clear the Site Preferences

• Options/Preferences -> Privacy & Security
  Firefox will: "Use custom settings for history":
  [X] "Clear history when Firefox closes" -> Settings
• https://support.mozilla.org/en-US/kb/delete-browsing-search-download-history-firefox

• clearing "Site Preferences" clears exceptions for cookies, images, pop-up windows, and software installation and exception for password and other website specific data
• clearing "Cookies" will remove all selected cookies including cookies with an Allow exception you may want to keep

Hello Parva,

Just in case non of the above do the trick, would you try this please :

Type in the address bar about:config and press Enter (promise to be careful, if asked)

Type in the search bar and look for the preference :

privacy.resistFingerprinting

Should the value be set to "true", change it to false (= default)

Then close and restart Firefox.

Be careful in changing about:config

font.size.systemFontScale with value 110 or 250 (very BIG FONT).

Next open new FF and joy with new bigger fonts, zoomed pages.