Guide
Fix "Failed to Verify Username" on Your Minecraft Server
Failed to verify username means the server checked the player's account with Mojang and the check failed. It usually happens when a player uses a non-premium launcher on a server with online mode on.
What online mode does
With online mode on, only players with a paid Minecraft account can join. With online mode off, launchers without a Mojang account can join too, and anyone can pick any name.
Change online mode in the panel
- Open your world and go to Settings.
- Under Online mode, click On or Off.
- Confirm. Changing online mode restarts the server and disconnects everyone online.
If you turn online mode off, use a whitelist
Without account checks, anyone who knows your address can join under any name, including yours. Turn on the whitelist and add your friends' exact names. See You are not whitelisted.
Player data after switching
Minecraft stores each player's inventory and position under an ID that is different in online and offline mode. If you switch an existing world, players can spawn with an empty inventory. Pick the mode before you start playing, and make a backup on Village or Kingdom before you switch.
Want to try this on a real server? Campfire is free and runs Vanilla. Village adds plugins, Kingdom adds mods and modpacks.