I is possible that Firefox is using a font for the user interface that looks very small.

You can check this with the Browser Toolbox.

• https://firefox-source-docs.mozilla.org/devtools-user/browser_toolbox/

• https://firefox-source-docs.mozilla.org/devtools-user/page_inspector/how_to/open_the_inspector/
• https://firefox-source-docs.mozilla.org/devtools-user/page_inspector/how_to/examine_and_edit_html/

You can check in the Rules tab in the right panel in the Inspector what font-family is used for selected text. You can check in the Fonts tab in the right panel in the Inspector what font is actually used because Firefox might be using a different font than specified by the website, if necessary expand "All fonts..."#. If the Fonts tab is hidden, click the Down arrow at the right end.

• https://firefox-source-docs.mozilla.org/devtools-user/page_inspector/how_to/edit_fonts/

No, it is not a function of the font family. I have tried various fonts. I'm a former typesetter, I know what I'm talking about. Other people have reported this same issue numerous times over the years, and the same about:config resolutions given by FireFox routinely fail to work. Surely after all this time you have come up with something that works reliably. I have some vision issues, but I shouldn't have to use a magnifying glass to see the text in the toolbars and menus.

Your reply above, about checking fonts in the Developer Toolbox, continues FF's record of futile nonsequitur responses. Nothing in the Fonts tab changes the size of the Fonts in the menus and toolbars. The only changesare to the font size in the web page itself, which is not what I need.Perhaps you can suggest something that actually works?

You need to use the Browser Toolbox to be able to inspect the font in the tab bar and other parts of the user interface like I posted above. You need to enable this toolbox via the settings page of the regular browser tools (Ctrl+Shift+I and F1) like stated in the article.

• https://firefox-source-docs.mozilla.org/devtools-user/browser_toolbox/