# Minecraft Failed to Authenticate – Online Mode & Mojang Fix

Minecraft "Failed to authenticate your connection"? online-mode, Mojang/Microsoft session, premium account, firewall – fix authentication errors.

**Quick answer:** "Failed to authenticate" = **session validation failed**. Use premium account, `online-mode=true` in server.properties, server must reach Mojang session servers (don't block outbound).

**If you landed here:** "Failed to authenticate your connection", "Invalid session" or premium players can't join.

## Related

- [Connection timed out](/en/gameserver/minecraft/connection-timed-out)
- [Server won't start](/en/gameserver/minecraft/server-startet-nicht)
- [Paper vs Spigot](/en/gameserver/minecraft/paper-vs-spigot)
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