Problem with custom shortcut and Linux/Ubuntu?

Our add-on has more than 200,000 users, and very few of them (including me) seem to experience a bug where the add-on’s shortcut doesn’t work most of the time. The reports we got so far were all on Ubuntu Linux, so I assume it might be related to that. Is anybody aware of issues like this?

The add-on doesn’t use a common Ctrl+something shortcut, but rather one where you press the control key (Ctrl, Alt, etc) twice. For me, this very often doesn’t work on Firefox, while it does in Chrome.

I’m looking for ideas on how to approach this. I don’t want to open an issue at Firefox, as I have no simple test case and the issue is not 100% reproducible.

The original bug report is at, our add-on is this:

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Hey @daniel.naber!

Thanks for letting us know. I’ve reached out to our Firefox devs to see if this is something that they’ve already encountered and have ideas for or if it’s a new thing.

I’ll get back to you when I learn more, I hope we can figure this out soon!

Keep me posted on this thread as well if you learn something new related to it or find a way to reproduce it reliably.

Another thing that could be helpful is if your users reporting the issue could test if it also happens on 105 that released yesterday. That might help us triage the issue.

I can confirm the issue still happens with 105. It’s not a new issue, it has been there for quite some versions of Firefox (it has always been there for me since we added that shortcut).

How does this work? You monitor for keydown or keyup of that individual key and if you see it twice in a row (without being combined with anything else?), then you run a script?

If you enable logging solo modifier keys on my test page, do you notice any issue with the script in the page detecting the keys on your Firefox or any others that have this issue?

We monitor for keyUp events and if there’s another even within 400ms, we run our code.

Your test page works fine.