Does anybody know how to break on a XHR request on Firefox developer tools? Earlier in firebug I added breakpoints under Net panel. As the firebug is discontinued any workaround for Firefox developer tools is appreciated.
That's currently (Firefox 57.0) not possible. It's requested in bug 821610.
Also other Break on… features like breaking on DOM mutations and breaking on cookie changes are still missing.
Those features are given high priority for implementation regarding missing Firebug features.