How to install a Minecraft modpack from Modrinth or CurseForge

To install a Minecraft modpack, you need a launcher that reads the pack's file list and downloads every mod for you. In Alloy: open Discover, search for the pack and choose Install pack, or import a .mrpack or CurseForge .zip from a file or link. Alloy creates the instance, installs the right Minecraft version, loader and Java, and downloads every mod.

What a modpack file is

A modpack is a list, not a pile of mods. The two common formats are:

• .mrpack (Modrinth): a zip with modrinth.index.json, which names each file, where to download it and its hash, plus an overrides folder for configs and anything else the author ships.
• CurseForge .zip: a zip with manifest.json, which names each mod by its CurseForge project and file number, plus overrides.

Both also name the Minecraft version and the mod loader (Fabric, Quilt, Forge or NeoForge) with its version. A launcher has to match all of them exactly, or the pack won't start.

Install a pack from Discover

1. Open Discover in Alloy and choose Modpacks.
2. Search for the pack, or open its page to read the description and pick a specific version.
3. Choose Install pack. Progress shows on the button and in the downloads panel, with sizes and time left.
4. When it's done, the pack is in your library. Press Play.

Install a pack from a file or a link

1. Choose New instance, then Import a modpack.
2. Paste a link to a .mrpack or CurseForge .zip, or choose the file. You can also drop the file anywhere on Alloy's window.
3. Alloy reads the format from the file's contents, not its extension, so a renamed file still works.

What happens during the install

• The right Java is downloaded for that Minecraft version, separately from any Java on your PC.
• The loader is installed. Forge and NeoForge run their official installers; the first instance of a version takes about half a minute to patch, later ones are instant.
• Every mod is downloaded and checked against the hash the pack lists, so a broken or swapped file never makes it in.
• Resource packs and shaders go into their own folders, even when a CurseForge pack lists them as mods.

When some files can't be downloaded

Some CurseForge mod authors don't allow launchers to download their files. Those mods have to come from the CurseForge website. Alloy lists each one with its download page and picks it up from your Downloads folder as soon as it lands, checked against its hash. Why this happens, and the quickest way through it.

Before the first launch

Give the pack enough memory. Alloy suggests an amount from the number of mods; for most packs of 100 to 200 mods that's 6 GB. How much RAM to give Minecraft.

When you press Play, Alloy checks the pack's mods against each other first, so a pack with a missing dependency tells you what's wrong instead of crashing. Fixing missing dependencies.

More guides

• Fix “requires Fabric API” and other missing mod dependency crashes
• Why some CurseForge mods have to be downloaded by hand
• How much RAM should you give Minecraft and modpacks?