Few things are more frustrating than trying to join a Minecraft server and getting an error. This guide covers every common connection issue and how to fix it, whether you're a player trying to join or a server owner diagnosing problems.
"Connection Refused" or "Can't Reach Server"
This means your computer can't establish a connection to the server at all.
For players:
Double-check the server IP address — even one wrong character will fail. Make sure you're including the port if it's not the default (e.g., play.example.com:25566). The server might be offline — check its status on MC-Servers.io to see if other players can connect. Try disabling your firewall temporarily to test. If you're on a school or work network, Minecraft's port (25565) may be blocked.
For server owners:
Verify your server is actually running in the console. Check that port 25565 is forwarded correctly in your router settings. Make sure your hosting provider's firewall allows inbound connections on the server port. Test locally with localhost first — if that works, the issue is network configuration.
"Outdated Client" or "Outdated Server"
Your Minecraft version doesn't match what the server is running.
Fix: Check which version the server requires (listed on MC-Servers.io or the server's website). In the Minecraft Launcher, go to "Installations" → "New Installation" → select the correct version. Many servers run 1.8-1.21 via ViaVersion, but some require a specific version.
If you see "Outdated server," the server hasn't updated to the latest Minecraft version yet. You'll need to create an installation with the older version, or wait for the server to update.
"Failed to Verify Username" / "Authentication Servers Are Down"
Mojang's authentication servers are either down or unreachable from your network.
Fix: Wait 5-10 minutes and try again — Mojang auth outages are usually brief. Check the Mojang status page or Downdetector. If it persists, try restarting your internet connection. Some ISPs have routing issues to Mojang's servers — try a VPN as a workaround. Make sure you're logged into the correct Microsoft account in the launcher.
"Connection Timed Out"
Your computer reached the server but didn't get a response in time.
Common causes: The server is overloaded with players. Your internet connection is unstable. The server is geographically very far from you (high ping). There's a temporary routing issue between you and the server.
Fixes: Try connecting again — sometimes it works on the second attempt. Reduce your render distance before connecting (Options → Video Settings → Render Distance: 8 or lower). Use a wired connection instead of Wi-Fi. Look for a server closer to your region using MC-Servers.io's country filters.
"You Are Banned" or "Kicked"
The server has specifically blocked your account or IP.
Banned: You violated the server's rules. Check the server's Discord or website for a ban appeal process. Be honest in your appeal — most servers will unban players who acknowledge their mistake. If you were falsely banned, provide evidence (screenshots, timestamps).
Kicked: Usually temporary — often for AFK, spam, or a minor infraction. You can rejoin immediately unless told otherwise.
"Invalid Session" / "Try Restarting Your Game"
Your login session has expired or become invalid.
Fix: Close Minecraft completely, then reopen the launcher and log in again. If that doesn't work, log out of your Microsoft account in the launcher, then log back in. Clear the launcher's cache by deleting the .minecraft/launcher_profiles.json file (it will regenerate).
"Server Is Full"
The server has reached its maximum player capacity.
Fix: Wait and try again — players leave constantly. Some servers offer "priority queue" for donors. Try joining during off-peak hours (early morning in the server's timezone). If the server is always full, look for similar servers with more capacity on MC-Servers.io.
"io.netty.channel" Errors
These are network-level errors that can mean many things:
Fix: Update your Java version (for Java Edition). Disable any VPN or proxy you're running. Add Minecraft as an exception in your antivirus software. Flush your DNS cache: open Command Prompt and run ipconfig /flushdns (Windows) or sudo dscacheutil -flushcache (Mac).
Performance Issues After Connecting
If you can connect but experience lag or disconnects:
Lower your video settings — especially render distance, particles, and entity distance. Install OptiFine or Sodium mod for better performance. Close other programs using bandwidth (streams, downloads). Check your ping to the server with /ping — anything under 100ms is good, over 200ms will feel laggy.
For more performance tips, read our server latency and ping guide.
Still having issues? Most server communities have Discord support channels where staff can help diagnose your specific problem. Find the server on MC-Servers.io and look for their Discord link.