2core
by Errnick_
2Core lets a single Fabric installation start and manage a second Minecraft server on the same machine, with both servers running as separate JVM processes.
What it does
The same mod JAR is installed on both servers, and each instance picks its role at startup. Once started, the secondary instance is handed its role through a system property and leaves out the process management logic. Installation needs Fabric API and Fabric Language Kotlin, and the mod copies itself into the secondary server's mods folder, so the second copy does not have to be installed separately. Server-side only; no client installation is needed.
Between the two servers, chat messages, join and leave notifications and death messages are relayed in real time, and the player list of the other server can be queried. Inter-server traffic runs over a TCP socket bound to localhost, so it is not exposed externally. Chat formats, color codes and player and message placeholders can be configured separately for each server. The mod is open source under the MIT License and is published for 1.21.11 only, with the 1.0.0 file dated 2026-05-20 as its first and latest release.
Key features
Process management
Start, stop and restart the secondary server from the primary with simple commands.
Cross-server chat sync
Chat, join and leave notices and death messages are passed between the two servers as they happen.
Player list queries
The primary server shows the online players of the secondary server, and the reverse is possible too.
Console relay
The secondary server's console output can optionally be mirrored on the primary server.
Auto-start
The secondary server can optionally start automatically when the primary server starts.
Configurable messages
Join, leave, chat and death message formats are set independently per server, with color code support.
Compatibility
Latest build for each game version and loader.
Only full game releases are shown. This mod publishes no snapshot builds.
Requirements
Dependencies declared by the latest file for each loader.
Required 2
How it compares
Mirage Sync is a Fabric mod for 1.21.11 under the MIT License, with a server required and client optional environment, and it is open source. Blocketing is server-side only, open source under the MIT License, and covers 1.21.5 – 1.21.10. Secondary Key is client-side only, covers 26.2 – 26.3, and is not open source under its MIT License.
| Mod | Loaders | Game versions | Environment | Updated |
|---|---|---|---|---|
| 2core | Fabric | 1.21.11 | Server-side only | 2026-05-20 |
| Mirage Sync | Fabric | 1.21.11 | Server required, client optional | 2026-04-25 |
| Blocketing | Fabric | 1.21.5 – 1.21.10 | Server-side only | 2025-10-25 |
| Secondary Key | Fabric | 26.2 – 26.3 | Client-side only | 2026-09-15 |
Questions
Does 2Core need a proxy or plugins to run two servers?
Is the second server's mod installed separately?
Can the inter-server connection be reached from outside the machine?
In the catalog
2core is one of 8,016 Management mods on ModsFinder, and one of 5,930 Management mods for Fabric. 19,862 mods support Minecraft 1.21.11.
More from Errnick_
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What the author says
Run a second Fabric server as a separate JVM process — one mod, two roles. 2Core lets you run two Minecraft servers on the same machine from a single mod. The primary server launches and manages the secondary server as an external JVM process. Both servers use the same mod JAR — the role (primary or secondary) is…
Official listing
- Modrinth page
- modrinth.com/mod/2core
- Owner
- Errnick_
- Published
- 2026-05-20
- Updated on Modrinth
- 2026-05-20
- Facts verified
- 2026-10-15