Open the debugger

There are three ways to open the debugger:

  • Select "Debugger" from the Web Developer submenu in the Firefox Menu (or Tools menu if you display the menu bar or are on Mac OS X)
  • Press Ctrl + Shift + Z on Windows and Linux, or Cmd + Opt + Z on macOS (starting in Firefox 71; prior to Firefox 66, the letter in this shortcut was S).

  • Press the menu button ( new fx menu ), select "Developer", then "Debugger".