Firefox debugger breakpoint not working

Question

When I click on a line to set a break point, the break point line gets highlighted, then the break point highlight disappears.

Other than that, Firefox developer debug has been working fine.

Answer 1

This might help people in the future without having to modify any js file:

Have you clicked the Deactivate breakpoints button? Pressing this will toggle breakpoints on/off.

If the icon is in blue, it means the breakpoints will be de-activated.

Note: I have noticed that in some sessions the toggle is activated although not blue, a refresh of the page solved this.

Answer 2

This just happened to me in Firefox 60.3.0. The tip about removing the Mozilla folder led me to a better solution, which is to edit the prefs.js file in the Mozilla profile folder. (In my system this was in C:\Users\xxx\AppData\Roaming\Mozilla\Firefox\Profiles\xxx.default)

I deleted all of the lines in prefs.js that began with

user_pref("devtools.

e.g.

user_pref("devtools.toolsidebar-height.inspector", 350);

user_pref("devtools.toolsidebar-width.inspector", 350);

This fixed the problem while preserving all my bookmarks, saved passwords, etc. The lines in prefs.js were recreated when I next ran the debugger.