How do I install and distribute a packwiz modpack?

packwiz modpacks are installed by pointing a launcher at a pack.toml file served over HTTP, usually through the Java-based packwiz-installer for MultiMC or ATLauncher, which keeps the instance updated automatically. The same pack can also be exported as a CurseForge or Modrinth modpack if you want to publish through those platforms instead. This guide covers the distribution options and the steps for each.

What packwiz actually distributes

packwiz is a command line tool for creating Minecraft modpacks. Rather than managing JAR files directly, it stores mod information as TOML metadata files (pack.toml, index.toml, and per-mod mod.pw.toml files) that are easy to version-control and share with Git. The actual mod JARs are referenced by URL and downloaded by the client at install time.

That design is what makes automatic updating possible: the client reads the metadata, compares it against what it already has, and fetches only what changed.

Option 1: packwiz-installer (auto-updating instances)

This is the recommended path for servers and for anyone who wants players to stay in sync without manual re-downloads.

Prerequisites

• A launcher that supports pre-launch commands: MultiMC or ATLauncher.
• The pack metadata reachable over HTTP (a web host, or a local packwiz serve instance for testing).
• Java available to the launcher, since packwiz-installer is Java-based.

Steps

1. Host the pack so pack.toml is available at a URL.
2. In MultiMC or ATLauncher, open the instance's settings and add a pre-launch command that runs packwiz-installer against that URL.
3. Launch the instance. The installer reads the metadata, downloads the listed mods, and places them in the instance.
4. On later launches, the same command runs again and applies only the changes, so updates are fast.

What you get

• Optional mods are supported, so players can opt in or out of specific files.
• Fast automatic updates, which is the main reason this setup suits servers.
• Server-only and client-only mod handling, so each side gets the correct set.

Common snags

• If the metadata URL is wrong or unreachable, the installer has nothing to read — verify the URL in a browser first.
• Because the installer is Java-based, a missing or mismatched Java runtime in the launcher will stop it before any mods download.

Option 2: HTTP distribution with a local test server

You can distribute the pack from any HTTP server. For testing before you publish, packwiz includes a built-in local server via packwiz serve, which lets you confirm the installer works against your own machine before pointing players at a public URL.

A practical order of operations:

1. Build the pack and confirm the metadata is correct.
2. Run packwiz serve locally and test the installer against the local URL.
3. Once it works, upload the same files to your real HTTP host and update the URL in the launcher command.

Option 3: Export to CurseForge or Modrinth

If your goal is public distribution rather than a private server pack, packwiz can export the pack to a CurseForge or Modrinth modpack. Those exports are then published through the respective platform's normal process.

Choose this when:

• You want the pack discoverable on CurseForge or Modrinth.
• Your players prefer installing through those platforms rather than a launcher pre-launch command.

Choose packwiz-installer instead when:

• The pack is private, for example for a server community.
• You need automatic updates and optional mods.

Which distribution method fits

What packwiz is not for

Two limits are worth knowing before you commit:

• Managing downloaded mod files. packwiz tracks metadata, not a local JAR library; use CurseForge, GDLauncher, or another CLI for that.
• GUI users. packwiz is a command line tool. Third-party GUI efforts exist but are not part of the core tool.

If either of those is a hard requirement, a different modpack workflow will serve you better.