Firewall Instructions

Many companies protect against outside attackers by shielding computers or their networks with firewalls to only allow certain traffic.

Therefore, you might experience that Butter is not accessible either to you as a host or to the guests you've invited to your session.

If your participants experience these firewall issues, we recommend running a trial session with one of the future guests before you schedule and plan the entire workshop.

If you work at a company where you want to get Butter whitelisted, you can share this guide containing instructions for your IT department:

Option 1

The best option is to not have any VPN and firewalls that block the usage of Butter, but this might not be possible.

Option 2

If you're on corporate WiFi, you might be inside a corporate VPN and firewall.

We would suggest asking your organization’s IT team to add this list of domains to their “Allow” list:


The first four make up our core infrastructure. The Twilio and Xirsys domains are TURN relay providers that we use to route audio and video for users behind firewalls.

Option 3

Firewalls can also be configured to allow UDP hole punching to the following ports: 40000 - 65534 for audio and video.

Usually, we don't need this, as Option 2 should work well.