By default, Firefox will follow your Windows "text size" setting. This may now default to 125% on new systems.

To check whether Firefox is using the Windows "text size" or a custom value, please try this:

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

(2) In the search box above the list, type or paste pix and pause while the list is filtered

(3) Check the layout.css.devPixelsPerPx preference:

• If it's bolded and "user set" to a numeric value, right-click it and choose Reset to restore the default value of -1 (that uses the Windows text size percentage).

• If it is already set to the default, try raising it above 1.0 to a value such as 1.25 or 1.5 to see whether that helps. You can double-click the preference to display a pop-up dialog to enter the new value. For the time being, focus on the toolbar area and ignore the content area, since you can adjust the zoom for that area.

Please avoid setting the value to any positive number smaller than 1.0 because if the number gets too low, you may no longer be able to use about:config to change it.

Can you find a good value?

Oh... if you installed the Theme Font & Size Changer extension, then its settings may be overriding the built-in settings. Look for its "A" icon to access the sizing options.

Note that the (global) Zoom setting in Theme Font & Size Changer modifies the layout.css.devPixelsPerPx pref and thus has the same effect as modifying the prefs on the about:config page.

Try to set layout.css.devPixelsPerPx to 1.0 (default is -1) on the about:config page. You can adjust its value in 0.1 or 0.05 steps (1.1 or 0.9) until icons or text looks right.

You can look at the Default FullZoom Level or NoSquint extension to set a default font size and page zoom on web pages.

• https://addons.mozilla.org/firefox/addon/default-fullzoom-level/
• https://addons.mozilla.org/firefox/addon/nosquint/