Manage Slack connection issues

This article is for IT or network administrators in charge of managing an organisation’s network. If you ever need a hand with troubleshooting connection issues, we're here to help.

If you’re not a network admin, check out our guide for troubleshooting Slack’s most common connection issues.


Desktop app

Older versions of the Slack desktop app can result in connection issues and even broken features. 


Network settings

Slack must have a persistent connection between our messaging server and members’ apps or browsers. To do so, Slack uses WebSockets over port 443.

Proxies and firewalls can sometimes interrupt this connection. If someone using Slack can’t connect from a specific location, or if there’s a WebSocket failure in our Slack connection test, you’ll need to adjust your proxy or firewall to keep the connection to Slack open. Here’s how:

  • Visit and add all specified URLs to your allowlist. If your environment requires access to multiple workspaces and/or orgs, visit that page from each workspace and/or org.
  • Check if your proxy is running SSL decryption. If it is, the proxy must either support WebSockets, or you’ll need to exempt the following domains:

Network administrators can restrict access to specific Slack workspaces using proxy header injection on their network. The header injection solution has the same network requirements as above. 

Network environment

Certain software, security settings and firewalls can interfere with Slack connections:


  • Avira Browser Safety
  • Browser Guard
  • Pokki
  • Smart Panel
  • Spyware and adware
  • Visual Discovery by Superfish

Antivirus or ad-blocking software

  • Avast
  • McAfee
  • Norton
  • AVG
  • AdBlock Plus

Temporarily turning off your antivirus or ad-blocking software may help you to troubleshoot your connection issue. If this fixes the issue, check to make sure that Slack is allowed by that software.

Still having problems? If you’re unable to resolve your connection issue, get in touch and include a Net Log if possible. 

Check connections

  1. Sign in to your Slack workspace.
  2. Visit to check your network’s connection to Slack.
  3. Under the WebSockets section, note the results for WebSocket (Flannel [Primary]) and WebSocket (Flannel [Backup]).

    • A successful test will show the  ticked circle icon.
    • A failed test will show the   warning icon.
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