hello, you can try the following to adapt the zoom level of the whole browser: enter about:config into the firefox address bar (confirm the info message in case it shows up) & search for the preference named layout.css.devPixelsPerPx. double-click it and change its value to 1.2 to set the size at 120% for example (or any other zoom factor that fits your purpose: 1.0 relates to 100%, 1.5 equals 150% and so on; -1.0 is the default value and will adhere to the system settings).

Thank you for you prompt reply. the setting you advised to change was set at -1. I amended it to 1.2 which resulted in the address bar and toolbar being enlarged, but it had no effect on the 'file' view and edit drop down text size.

I think the solution is a 60" TV, but hopefully we can find a more affordable workaround!

I think the top menu bar on MacOS X --

[Apple] Firefox File Edit View History Bookmarks Tool Window Help

-- might not be amenable to changes through a Firefox setting or add-on.

However, as Windows user, I'm at a disadvantage in experimenting.

I did see a number of threads on Apple's forums, without a clear satisfactory solution:

• How do I increase the size of fonts in Yosemite? | Apple Support Communities - links to articles with suggestions
• How do I increase font size on the menu bar and... | Apple Support Communities - said contacting Apple support resolved the problem (didn't mention Firefox, though)
• Yosemite: how to increase menu font size? | Apple Support Communities - suggests a font change, plus much other discussion

i clicked on the links you provided . . . . I see I am not the only one with this problem (109 others have the same one!). So I have poured a beer and am going through the answers! Thank you.