Managing Mods

Mods are declared in the mods block of mc.kdl, grouped by source, and installed when the instance starts. Under modrinth, each node names a mod by its identifier on the mod registry and pins the version to install:

minecraft {
    version "..."
    loader "fabric"
}

mods {
    modrinth {
        lithium "..."
    }
}

A mod loader must be configured under minecraft for mods to be installed; without one, the mods block is ignored. See The Manifest Format for the other groups, including mods fetched from a direct URL.

Adding and removing mods

mc add and mc remove edit the modrinth group for you. mc add looks the mod up on the registry and pins the latest version compatible with the configured Minecraft version and loader:

mc add sodium lithium
mc remove sodium

Updating mods

mc update re-pins mods to the latest compatible version — every mod in the manifest, or only the ones you name:

mc update
mc update lithium

Mods fetched from a direct URL have no version to compare and are skipped.

How mods are installed

Changes to mods take effect the next time the instance starts. On startup, mc resolves each entry — including its required dependencies — and records the result in the mc.lock lockfile. It then downloads any mod that is missing and deletes any mod that is no longer in the lockfile.

Two consequences of this are worth knowing:

• You do not need to declare a mod’s dependencies; they are resolved and installed automatically.
• The instance’s mods directory is fully managed by mc. A jar placed there by hand is removed on the next start. To install a mod that is not on the registry, declare it in the manifest under the http group instead.