Bring your own world
Open a saved world and the co-op lobby, choose your traveler name and host explicitly. Hub-backed sessions use the configured Solaria server to route connection and invitation traffic. Keep the host game open: the hub does not simulate, own or migrate your save.
Share the code privately
Send the host’s ten-character invite code to friends. Guests use Join Co-op and enter that code. A code is access information, not a profile identity; do not post it on public rankings or in screenshots. The game validates protocol compatibility and capacity when connecting.
Keep ownership clear
The host validates gameplay. Inventories and remembered NPC relationships remain separate travelers. Placed blocks are private by default; share a target explicitly when you want guests to use or modify it. Menus do not pause a co-op world.
Know the trust boundary
Use HTTPS/WSS for the deployed hub. TLS protects transport between each client and the server; relayed game traffic is not end-to-end encrypted from the server operator. Direct LAN play has its own trusted-network requirements. Server availability never guarantees host availability.
Mechanics reference
Original guide prose, checked against these game source catalogs for 1.53.0 · build 70:
multiplayer/COOP_PLAY.md
Actual in-game costs, compatibility and confirmations take precedence if your installed version differs.