How to disable alt+scroll wheel?

Hi, you can install a extension that can modify and change your hotkeys such as 'Shortkeys'. There's also an answer to a question similar to yours that shows you how you can modify firefox to disable all hotkeys: https://support.mozilla.org/en-US/questions/1302854#answer-1347520

Goodluck

here are specific actions defined to set what happens if you rotate the mouse wheel and hold down modifier keys like Alt or Ctrl or Shift. You can disable this action by setting the related mousewheel pref to 0 (zero) on the about:config page.

• mousewheel.with_alt.action = 2, change to 0

Action:

0: Nothing happens
1: Scrolling contents
2: Go back or go forward, in your history
3: Zoom in or out (reflowing zoom)
4: Treat vertical wheel as horizontal scroll
5: Zoom in or out (pinch zoom)

You can open the about:config page via the location/address bar. You can click the button to "Accept the Risk and Continue".

• https://support.mozilla.org/en-US/kb/about-config-editor-firefox