Didn't they change it so it's much more similar to how Chrome extensions work? Shouldn't it in fact be easier now to have an extension work in both Chrome and Firefox? The Mozilla wiki page on WebExtensions even says "Much of the specifics of the new API are similar to the Blink extension API."
The Chrome extension used should work just fine with Firefox, but Google would rather try and force vendor lock-in. At this point I just use Jitsi, it works every time without any browser extensions to do a quick video conference or screen share.
When it launched in 2013, Hangouts used an NPAPI plugin that worked in most browsers. In 2014, Google ported Hangouts to WebRTC for Chrome only because it relied on non-standard WebRTC features only implemented in Chrome. Note that Firefox did support WebRTC at this time and Mozilla in fact developed its own WebRTC video chat service in 2014 called "Hello" that worked in Firefox and Chrome.
In 2015, Mozilla announced that it would drop support for NPAPI plugins in 2017, giving websites using NPAPI plugins ~18 months to switch to a non-plugin solution. When the NPAPI deadline came, Google announced the Hangouts would stop working in Firefox, they were "actively working to develop a solution" for Firefox, and until then Hangouts users should use another browser:
It's 2018 and Google is still working to support WebRTC in Firefox, but they're definitely working on it. In fact, WebRTC Hangouts does mostly work in Firefox now, but only for users with a G Suites enterprise account whose admin has manually enabled Hangouts. I don't know why.
"Hangouts Meet" is a different product using WebRTC whose support for Firefox is still in development.
I've been documenting this saga on this Mozilla wiki as part of the NPAPI deprecation and Win64 Firefox rollout:
Since October 30 2016, Hangouts is unusable on me on Safari.
I always use the pop-up feature in order to get individual chat windows that are real operating system windows, rather that the javascript windows in Gmail. Since that date, it doesn't work in Safari. It works for a few minutes, then the windows close themselves and disappear.
The only solution was to use Chrome... which worked until very recently. Now I get the same problem with Chrome too, albeit the timeout is much longer, perhaps an hour or so or sometimes longer.
Everything is fucked.
By the way, this is Apple bug 29018740. It might help if someone makes another bug report and references this bug, though I doubt it because when the latest Safari version was released (with the bug still present, of course), I mentioned this to Apple and they responded:
> Thank you for contacting us. If this is still an issue for you on current releases, please file a new bug report.
Thanks Apple.
By the way, this is just for text messaging. For voice/video Hangouts became unusable earlier than that. The video quality is approximately 120p and the audio is 1kbps or less, and I can't talk because noise cancellation doesn't work and I hear myself back with a 2 second delay and 80dB gain. Don't even get me started on CPU utilization yet...