User Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:65.0) Gecko/20100101 Firefox/65.0 Steps to reproduce: 1. Open a web page with some sort of readily-triggered exception. 2. Open the Debugger tab of the dev tools. 3. Ensure “Pause on exceptions” is turned on. 4. For good measure, even add a breakpoint on a line that is definitely run. 5. Just to make absolutely sure, add a line `debugger` before the exception. Actual results: The exception is thrown. The debugger doesn’t stop at any point. Expected results: It should have stopped at the breakpoint, the `debugger;` statement and the exception. This is a regression from the last couple of weeks or so. It’s not *quite* consistently reproducible: I have another thing on the file: scheme using ES modules (possibly significant, possibly not) where it *does* stop, but locks up the browser completely a second or two later, like it’s busy waiting on the UI thread or something, requiring a manual restart. That behaviour started at the same time. In short, the debugger is currently completely non-functional for me at present: either it doesn’t work, or it works and I wish it hadn’t. I’m using both https: and file: URLs to test this.

Hmm, could you provide a test case perhaps by forking http://dbg.glitch.me/?

(In reply to Jason Laster [:jlast] from comment #1) > Hmm, could you provide a test case perhaps by forking http://dbg.glitch.me/?

I can no longer reproduce it, so I presume it has been fixed. 👍

Turns out I was wrong; it is still a bug. I’ve opened bug 1516941 to replace this closed bug.