To increase the text size in the user interface parts of Firefox, we currently only have one setting option, which is the global scaling factor. Here's how you can adjust that if you want to give it a try:

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

More info on about:config: Configuration Editor for Firefox. The moderators would like us to remind you that changes made through this back door aren't fully supported and aren't guaranteed to continue working in the future. We have had this setting for a long time so I feel comfortable mentioning it.

(2) In the search box in the page, type or paste layout.css.devPixelsPerPx and pause while the list is filtered

Firefox should list one preference with the value -1.0

-1.0 means to follow the system level scaling. You can enter new (positive) values here to set your own scaling. Please note that the values will be doubled for a Retina display.

(3) Double-click the preference to display an editing field, and change the value to either

• 1.5 for non-Retina display
• 3.0 for Retina display

Then press Return or click the blue check mark button to save the change.

That should scale the entire browser to 150% of the default size.

You can adjust upwards or downwards as needed. Please be very careful not to use a value below 1.0 or it may become too difficult to read/fix. In case of emergency, click the reset button at the right end of the row.

Can you find a size that is comfortable for the toolbars/sidebar? Hopefully so. Then you can tweak the page zoom setting on the Preferences page to make the content area a comfortable size.

I made the changes that were recommended and it worked like a charm. I finally settled on a setting of 2.50 which seemed the most comfortable for my wife and I. Thanks!