How can I turn on accessibility features in Firefox?

Question

Firefox's developer tools has an Accessibility section that I'd like to use. However, the button to turn it on is disabled.

I've tried refreshing the page once the Accessibility tab is open but it hasn't helped. I'm using version 64.0.2 (Quantum) on macOS; have also experienced the same thing on Linux (unsure of versions).

Answer 1

Firefox disables it for some reason. Go to about:config in URL bar, then locate accessibility.force_disabled. Change the value for it from 1 to 0.

Answer 2

Firefox (like several other browsers) has been relentlessly optimised for performance. One of the performance tweaks consist in turning off the accessibility API by default, unless a running assistive technology is detected when the browser is launched.

In order to test this, you can turn on an accessibility features such as the Zoom/Magnifier on Windows or even simply High Contrast in the GNOME desktop on Linux. I found that turning on High Contrast in Gnome on Manjaro while Firefox was open already allowed me to turn on the Accessibility Features.