Forge
Minecraft with Forge mod loader
Single-Threaded Game
Minecraft is single-threaded. Allocate more memory and reduce view distance. Adding CPU cores won't help. Heavy modpacks need 4 to 8 GB RAM.
Pick the Right Java Version
Use Java 8 for MC 1.16 and older, Java 17 for 1.17 to 1.20.4, Java 21 for 1.20.5+. Mismatches usually surface as UnsupportedClassVersionError at startup.
Some MC Versions Have No Recommended Forge
For Minecraft versions without a "recommended" Forge build (e.g. 1.21.1), set Build Type to latest in the Startup tab.
EULA + RCON Auto-Wired
The EULA is accepted automatically on install. RCON uses the password and port from your Startup tab. You don't need to touch server.properties or eula.txt.
Official Documentation