I noticed when I pulled out my network or turned off wifi with a switch,
navigator.onLine does not turn false.

Application demonstrating the problem:
http://static.dabase.com/online/

I noticed a similar bug in upstream BTS:
https://bugzilla.mozilla.org/show_bug.cgi?id=426932#c28

IIUC there is some Network Manager integration, but I'm having
difficulty finding details of the integration. Tbh I prefer not to
integrate with crazy bloatware and I'm looking for an elegant solution
that cleanly applies to /etc/network/interfaces

Sidenote: Google Chrome 20.0.1132.57 also seems to have this problem btw.

Many thanks,

src:iceweasel has been superseded by src:firefox-esr in version
45.0esr-1 in March 2016. Transitional packages to ease upgrades were
provided in the wheezy, jessie, stretch and buster releases. The
transitional packages have been removed finally before the bullseye
release in August 2021.
After regular security support for buster ended in August 2022 and LTS
support ended in June 2024, I'm closing the remaining bug reports now.

Andreas