Failed to verify username! / Invalid session
JOIN-006 · Failed to verify username
'Failed to verify username!' or 'Invalid session (Try restarting your game)' when joining a Minecraft server. Account verification problems, and why switching online mode off is the wrong fix.
What it looks like in the logFailed to verify username! Invalid session (Try restarting your game and the launcher) Authentication servers are down. Please try again later, sorry!
What it means
With online-mode=true, the default, the server asks Mojang's login service to confirm that each player really owns the account they claim. "Failed to verify username" means that check didn't succeed. "Invalid session" is the same thing seen from the player's side: their game has no valid login to prove.
How to fix it
- Restart the game and launcher, and sign in again. This clears most "Invalid session" cases, especially after the launcher has been open for days.
- Check whether Mojang's login service is down. If it is, nobody can join an online-mode server until it recovers. Wait a few minutes and try again.
- Check the server's clock and internet. The server has to reach Mojang to verify anyone. A badly wrong system clock or a blocked outbound connection from the server's PC causes failures for every player at once.
- Is it a non-purchased or modified launcher? Those accounts can't be verified, so an online-mode server will refuse them by design.
The tempting shortcut is to set online-mode=false. It works, but it switches off account checking entirely: anyone can join under any name, including yours or an operator's. If you must use it, keep the whitelist on and don't expose the server publicly, and expect player data to move, since offline players get different identities.
More help
Coalstack's Auto Debugger scans a Java server's log for known errors like this one and links straight to the fix. Download Coalstack to try it.