Run a custom server jar

The catalogue covers vanilla, Paper, Purpur, Spigot, Fabric, Forge, NeoForge, Mohist and the proxies. For anything else (a fork, a beta build, a private jar), run your own.

Set it up

1. Files: upload the jar into the server folder as server.jar.
2. Settings, General, Custom JAR: turn it on. Pick the Java version the jar needs; the default follows the Minecraft version, and a jar built for a newer Java will say so in the console.
3. Restart.

The memory flags are still set from the server’s RAM setting, so there is no start script to write.

When to use it

• A fork such as Leaf, Pufferfish or Folia that we do not list.
• A specific build of Paper or Fabric for a plugin that has not caught up.
• A modded server assembled by hand from a server pack whose loader jar you want to keep exactly as shipped, or a hybrid such as Arclight, on a server software other than Forge, NeoForge or Magma (see below).

Good to know

• A custom jar is not updated for you. Turn Custom JAR off to return to the managed jar and version switching.
• The server always starts server.jar from the server folder, so keep that name.
• On Forge, NeoForge and Magma, Custom JAR does not run your jar: the server still starts the loader FadeHost installs for its version, never on a Java below what that Minecraft version needs. To run a jar of your own, pick another server software while Custom JAR is off, then turn it on.
• Jars that need Java 8 (1.12.2 and older) work; the Java version field goes down to 8.