Couldn't Connect
Slack Software
Severity: MinorWhat Does This Error Mean?
Slack shows 'Couldn't connect' or 'We can't reach Slack right now' when the app cannot establish a network connection to Slack's servers.
Cause is usually local network — WiFi, captive portals, or corporate firewalls — but Slack itself does have brief outages.
Most cases clear within a few minutes by checking your internet, switching networks, or waiting if Slack's status page shows an incident.
Affected Models
- Slack desktop on Windows
- Slack desktop on Mac
- Slack desktop on Linux
- Slack iOS app
- Slack Android app
- Slack in browser
Common Causes
- Local internet connection down
- Captive portal at hotel or coffee shop blocking traffic
- Corporate firewall blocking Slack domains
- VPN routing breaking Slack's connection
- Slack itself in an incident (rare but happens)
- DNS server not resolving slack.com
How to Fix It
-
Check internet on another app.
Open a web page or another app that uses internet.
If those work, Slack is likely the issue.
If they fail too, fix the local network first. -
Check Slack's status page.
Visit status.slack.com from a phone or browser.
If Slack reports an incident, you cannot fix it from your end — wait for the resolution.
Most Slack incidents clear within an hour. -
Switch networks.
Try mobile data instead of WiFi, or vice versa.
If Slack works on mobile but not WiFi, the WiFi network is blocking it — captive portal, firewall, or DNS issue.
Open a browser and load slack.com directly to check. -
Disable VPN temporarily.
Some VPN services route Slack traffic in ways that break the connection.
Disconnect the VPN and try Slack again.
If it works without VPN, contact your VPN provider — Slack publishes a list of IP ranges that VPNs need to allow. -
Restart the Slack app.
Quit Slack completely.
On desktop: Cmd+Q (Mac) or close from system tray (Windows).
On mobile: swipe up from recent apps.
Reopen.
Many transient connection failures clear here. -
Switch DNS to public servers.
If your ISP DNS is flaky, switch to 8.8.8.8 (Google) or 1.1.1.1 (Cloudflare).
On Mac: System Settings → Network → Advanced → DNS.
On Windows: Control Panel → Network → Adapter Settings → IPv4 Properties.
This fixes a meaningful share of intermittent connection failures.
Frequently Asked Questions
Why can I open slack.com but not the app?
The Slack app uses different protocols than the website — WebSocket connections for real-time messages, plus several API endpoints.
A network can allow web traffic while blocking some of the app's specific endpoints.
Browser sometimes works when app fails for exactly this reason.