Screenshot of what your asking to change?

MSWS said

I'd like to disable / being Quick Search, is there a way to do this without installing add-ons or third party software?

Is that the Quick Find feature which is activated with the / key?

Firefox's doesn't have any built-in features to modify or override keyboard shortcuts, although in some cases it may be possible to disable the feature associated with the keyboard shortcut (at least it used to work that way in Developer Tools).

Even with an add-on, it may not be possible to prevent / from opening QuickFind in all cases. For example, in Google's calculator embedded in the search results page (I can't recall where that thread was).

One add-on option is a user script. User scripts are applied to pages using one of the "monkey" extensions. As with any add-on, you need to be careful with the scripts you install.

If you want to try the user script I posted, you'll need the Greasemonkey extension first, then you can install the script:

• Script: https://greasyfork.org/en/scripts/13484-prevent-slash-opening-quickfind

• Extension options:
  • Violentmonkey (I currently use this one): https://addons.mozilla.org/firefox/addon/violentmonkey/
  • Tampermonkey: https://addons.mozilla.org/firefox/addon/tampermonkey/
  • Greasemonkey: https://addons.mozilla.org/firefox/addon/greasemonkey/

By the way, the developers have added a preference for this to the development version of Firefox (Nightly), which should be released in a a few months as Firefox 63. It might make its way into the next major release of Firefox (Firefox 62).

For reference, in Nightly, setting accessibility.typeaheadfind.manual to false disables / and ' from calling up the QuickFind bar.

If any readers are interested in running test versions of Firefox, which are less stable than the release version, see: https://www.mozilla.org/firefox/channel/desktop/