How to update a modpack without losing your world (and roll back if it breaks)

Yesterday the pack worked. Today, after the launcher updated a few mods, it crashes on launch, or worse, it loads and half your base is missing. Mod updates are the quiet killer of long-running packs. Here's how to recover, and how to stop it happening again.

First: don't open the world again

If the pack starts but your world looks wrong (missing blocks, empty machines, items gone), quit, and don't load that world again until you've backed it up. Plan to restore a backup from before the update rather than trust the current save. When Minecraft loads a world and finds blocks or items from a mod that's missing or changed, it can drop them, and once the world saves, they're gone for good.

Back up the world

Copy your world folder somewhere safe before doing anything else. It's in your pack's folder, inside saves/. Copy the whole world folder, not just parts of it. If you play on a server, stop the server and copy its world folder.

If your launcher or server keeps automatic backups, find the most recent one from before the update. That's the one you want.

Roll back the mods

You want the exact mod versions you had before. How to get them:

• If it's a published modpack: install the previous version of the pack. Both the CurseForge app and Modrinth App let you choose an older pack version.
• If it's your own pack: check your launcher for the mod versions you had. Some launchers keep a history or let you pick a mod's version from a list. Mod pages on CurseForge and Modrinth keep every older file.
• If you exported the pack before: re-import that export. It records exact versions.

Then restore the backed-up world from before the update, and launch.

Find out what the update changed

Before you try updating again, find out what broke:

• Read the updated mods' changelogs. Look for words like "removed", "renamed", "rewrote", "breaking" or "not compatible with old worlds".
• If the pack crashed, read the crash report. See how to find the mod causing a crash.
• Check whether the update needs a newer version of another mod. Mods often update in step with their libraries.

Update without breaking things next time

• Turn off automatic updates for packs you care about.
• Update on purpose, a few mods at a time, not everything at once.
• Back up the world before every update. Every time.
• Test on a copy. Load a copy of the world first, look around your base, check machines still run.
• Update everyone together on a server, or players won't be able to join.

How Packspire handles updates

This is a big part of what Packspire does. Packs are pinned to exact versions, so nothing changes behind your back. When you update, Packspire rebuilds the pack with the new versions and runs every test again: it starts the server and the game, plays a world, and rechecks the recipes. An update that crashes is held back automatically and the working version stays. Each build writes a changelog of which mods changed and every recipe added, removed or changed, and if an update would remove items, it tells you to back up your world and how many items from each mod will disappear.

Build a pack that updates safely.

Frequently asked questions

How do I update a modpack without losing my world?

Back up the world folder from saves/ first, read the changelog for removed mods or items, update the whole pack (not single mods), and open a copy of the world before your real one. If anything is missing, restore the backup and stay on the old version.

How do I downgrade a modpack in the CurseForge app?

Open the profile's settings and choose an earlier version of the pack, or change an individual mod's file to an older version. Back up the world first.

Can a mod update delete blocks from my world?

Yes. If an update removes or renames blocks or items, Minecraft drops them when it loads those parts of the world, and once saved they're gone unless you restore a backup.

Should I turn off automatic mod updates?

For a pack you care about, yes. Update on purpose, a few mods at a time, after backing up and testing on a copy of the world.

Where are Minecraft worlds saved in a modpack?

In the pack's instance folder, inside saves/, one folder per world. A server's world is the folder named in its server.properties, usually world.

Sources

• CurseForge and Modrinth, which keep every older file of a mod