Troubleshoot Slack Calls

If you happen to run into issues with Slack’s call features, you can test your calls connection by visiting Read on to learn more about additional troubleshooting steps for connection, audio, and video errors.


Calls connectivity test

Begin troubleshooting by testing your calls connection with your diagnostic tool. The results will indicate where the issues may be occurring. If your issue is still not resolved, keep reading for some common fixes. Or reach out to us — we're here to help! 

Connection errors 

There are two common connection issues: trouble connecting to a call or trouble connecting to the server. If you're experiencing one of these issues, here are some recommendations that may help. 

Tip: When it comes to connection trouble, firewalls are the most common culprit. 🔥

Call connection errors

If Slack is having trouble establishing a call connection, give these tips a try:

  • Check that your network is set to allow outbound UDP connections to port 22466 and whitelist *
  • If the above isn't possible, you'll need to allow TCP on port 22466 on *
  • If neither of the above is an option, you'll need to allow HTTPS on port 443 (optionally using an HTTPS proxy) on * Your IT team should be able to assist in setting this up.

Note: If your firewall doesn’t allow whitelisting wildcards (like *, your IT team can try writing a script that polls on a regular basis (e.g. once every 5 minutes) to get a list of active servers to whitelist.

Bandwidth requirements

Here's a list of bandwidth requirements for optimal performance: 

Type of call  Download speed  Upload speed 
 Voice call  200 kbps  100 kbps
 Video call* (2 participants)  600 kbps  600 kbps
 Video call* (3 participants)  2 Mbps  600 kbps
 Video call* (5+ participants)  4 Mbps  600 kbps

*Requirements are the same for screen sharing.

Server connection errors

If you're trying to make a call but Slack is having trouble connecting to the server, open in a browser.

If does not load, check that your network is set to allow outbound TCP connections to port 443. This should fix things.👌

If does load, but you're still having trouble making a call, contact us and we'll investigate further. 🕵

Audio errors 

If you run into an audio issue during a call, have each participant use the tips below. 

  • Restart the Slack app, then try to make your call again.
  • Check your device’s system preferences: confirm that audio isn't muted and the correct input and output device is selected.
  • For those using Slack on a desktop: check the call's audio settings by clicking the   gear icon in the call window. Make sure the correct input and output device is selected.
  • For those using Slack in Google Chrome: quit Chrome, relaunch your browser, and then reopen Slack.


Video errors 

Having an issue with video or screen sharing? Try restarting Slack to see if that helps. If you're still having trouble, check out the sections below.

Video connection error

If the video on your call is out of sync, freezes, or disconnects, give the following a try:

  • Make sure you have a strong network connection.
  • Run a speed test to double check that your device's bandwidth meets the video call requirements.

Your video fails to display

If your video fails to display during a call, here's what you can do:

  • Are you using an external camera? Make sure to plug it in before you start a call. If it's plugged in after the call has started, your video will fail to display. 
  • You've plugged in your camera before starting the call, but you're still having trouble. Click the   gear icon in the call window to check your Video settings — make sure the correct camera is selected.
  • Still not resolved? Manually select a different camera using the same steps above, then switch back to your desired camera again. 
If your device is running macOS 10.15 and you’re having trouble sharing your screen, check your OS settings:
  1. Open your computer's System Preferences.
  2. Click Security & Privacy, then the Privacy tab.
  3. Locate Screen Recording on the left.
  4. From the app list, click the box beside Slack.

High CPU usage

If you notice your computer runs slowly when you're on a video call, this may be due to high Central Processing Unit (CPU) usage. For calls with many participants, we recommend turning video off when it’s not needed and re-enabling video when it is.