You can now open Browser Toolboxes on more than one instance of Firefox

Patrick Brosset pbrosset at
Mon Aug 28 07:58:24 UTC 2017

And big thanks to you Brian for making our dev workflows better!

On Fri, Aug 25, 2017 at 7:37 PM, Brian Grinstead <bgrinstead at>

> It used to be that if you opened the Browser Toolbox on more than one
> instance of Firefox, then all the Browser Toolboxes would end up connecting
> to the first instance. I know a lot of people have run into this problem,
> myself included. For instance:
>   ./mach run --profile /tmp/1 --jsdebugger
>   ./mach run --profile /tmp/2 --jsdebugger
> Here both Browser Toolboxes would end up debugging the first instance of
> the browser. This is because the debugger server used a static port (6080)
> so when the second instance tried to start the debugger server it would
> fail, but the Browser Toolbox frontend didn't care and just connected to
> 6080 (the first instance).
> I had an idea to make this better by letting you specify an explicit port
> for the second instance, but jryans had a much better idea, which was to
> randomly pick a port when starting the debugger server and send it along to
> the Browser Toolbox (
> show_bug.cgi?id=1392744#c2). So it should be working automatically now -
> you should see dump output like: `Debugger Server for Browser Toolbox
> listening on port: 63148` after starting it.
> Big thanks to Ryan, and happy debugging!
> Brian
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> firefox-dev at
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