Steamhearth

Play Minecraft with Steam friends without port forwarding, a public IP, or a dedicated server.

Steamhearth lets you open your singleplayer world to your Steam friends with as little setup as possible. Connections are handled through Steam P2P and Valve relays, so you do not need to configure your router, expose a public IP, or set up a separate Minecraft server.

Features

• Steam Friends integration
  See which of your Steam friends are currently hosting a world and join them directly.
• Join Game support
  Friends can use Steam's Join Game option or accept an invitation while Minecraft is running.
• No port forwarding
  Minecraft traffic is carried through Steam P2P and Valve relay infrastructure instead of requiring direct inbound connections.
• Automatic mod checking
  Steamhearth compares the host's and guest's required mods before Minecraft connects, avoiding failed joins caused by mismatched mod setups.
• Download missing mods
  Missing supported mods can be downloaded from official Modrinth or CurseForge sources. Downloads are verified before installation.
• Client-only mods are ignored
  Client-side mods such as shaders, minimaps, and interface tweaks do not need to match between the host and guest.
• Automatic restart and return
  After missing mods are installed, Steamhearth can restart Minecraft and automatically return you to the same host.
• Friends-only access
  By default, only the host's Steam friends can join. Guest identity is based on the authenticated Steam account rather than simply trusting the username sent by Minecraft.
• Automatic reconnection
  Temporary Steam P2P interruptions can be recovered without immediately dropping the Minecraft session.
• Voice chat support
  UDP traffic used by voice chat mods such as Simple Voice Chat can travel through a separate Steam connection.
• Built-in Steam diagnostics
  If Steam cannot initialize correctly, Steamhearth shows a diagnostic checklist instead of only giving a generic connection error.

How to use

Hosting

Open your singleplayer world and select:

Open to Online → Open to Friends → Start Session

From there, you can invite a Steam friend directly from the in-game friends list.

Joining

A guest can:

• Accept a Steam invitation
• Press Join Game from Steam
• Press Join next to a hosting friend inside Minecraft
• Connect manually using the host's Steamhearth address

Steamhearth checks the required mods before connecting. If something is missing, it shows what is needed and can download supported mods automatically.

Requirements

• Steam must be running and logged in.
• Your Steam account must have at least one game installed locally.
• Minecraft must already be running for Steam's Join Game feature to bring you into a friend's world.
• Both players need Steamhearth installed.
• Steamhearth currently targets Fabric.

Important

Steamhearth currently uses Steam's public Spacewar AppID 480 for Steam networking.

Because of this, Steam may show you as playing Spacewar while Steamhearth is connected. This is expected behavior.

Steam cannot launch Minecraft through AppID 480. This means Join Game works when Minecraft is already open, but it cannot automatically start Minecraft for the guest.

Open your world. Invite your friends. Play.