Breaking on exceptions

To instruct the debugger to pause on an exception, tick these checkboxes in the Breakpoints list:
  • Pause on exceptions
  • Pause on caught exceptions
Screen shot showing "Pause on exceptions" and "Pause on caught exceptions" checkboxes

When an exception occurs, the line where it occurs is highlighted in the source pane, with a squiggly red line under the problematic code. A tooltip describes the exception. Starting in Firefox 80, a disclosure triangle within the tooltip reveals a stack trace.

Screenshot of a tooltip for an exception