11 years after the bug was filed, Mozilla finally got to work on this popular feature request, and it seems to be working okay now (tested in Firefox 66.0.3/Ubuntu).
(Thanks to @PerJohansson for pointing out that they've made the setting much more difficult to find since FF 59.)
I've just updated this answer with some easier steps, tested with Firefox 75.
NOTE that if you'd like to disable shortcuts for all sites by default, navigate to
about:config, and set the value of
permissions.default.shortcuts to 2. Thanks to @inetknght for the tip, which is also documented here: https://support.mozilla.org/en-US/questions/1241294#answer-1175070
For disabling shortcuts on a per-site basis, you can find screenshots for each step below.
- Press Ctrl-I (if you can) to show the Page Info window; or else right-click on an empty portion on the web page, and select
View Page Info from the context menu.
- Select the
- Adjust the
Override Keyboard Shortcuts setting.
Here are some recent (April 2020) screen shots for each step.
- If you use the mouse to open the Page Info window:
- Select the
- Adjust the permissions appropriately:
Mozilla has more information on the
Page Info window here:
And if you're interested in the history of this fix, here are the related Mozilla tickets: