It’s a combination of a few things. First, when we started doing calls together Slack calls weren’t available yet for multiple people.

In our experience, Slack calls often fail for a variety of reasons. Other than that, we don’t want to shift too much data to Slack and since it’s pretty unclear how their calling technology works and appear.in uses WebRTC, we rather use another service here than a service where we don’t know much about it but only that calls aren’t too reliable. But as said, we haven’t bothered to check the group-video calling yet there. We’re pragmatic. Appear.in works in any browser (Slack calls don’t) and therefore… why should we change a well working system?

Slack’s audio/video conferencing feature sometimes double-connects an user and frequently connects without sending audio traffic either way.

My team has been using ScreenHero prior to Slack buying them out. ScreenHero also supports audio calls without screen-sharing, and its audio calls have not been problematic for us.

> It’s quite reliable and even offers screen sharing without any plugins on Firefox.

Since they bothered writing this, I guess the lack of support for Firefox.