How to keep a modded world from breaking

Nothing hurts like a modded world that won’t load anymore. A modded world breaks at a save. The save either no longer has the mods that built it, or a newer Minecraft version has already converted the chunks. The way back is a copy made before that save.

I play Minecraft 1.21.1 on NeoForge: Create 6.0.10, Aeronautics 1.3.2 (needs Sable), Big Cannons, Iron’s Spellbooks, Apotheosis, YUNG’s, Dungeons Arise, Sodium + Iris, JEI, Jade. We share the instance through the Modrinth App. That pack is Create Aeronautics. Here’s the order that keeps a save like that from being your only copy.

What you are about to change

What are you about to change?

Update the packRemove a modOpen it on another pack

Quit, copy the instance, and update the copy. The dated original stays closed.

A modpack is a set of jars plus the world those jars already wrote. A performance mod (Sodium on my instance) adds no blocks, so the world barely notices a swap. A content mod — Create machines, a dimension, a quest book — is the one that can empty part of the save if the jar is gone when you click Continue.

How to install a Minecraft mod is one jar for that loader and version. This guide is what you do before you touch the folder. The launcher row that starts the instance is the row whose folder you copy. Latest Release is the wrong folder.

Quit, then copy the instance

Save and quit. A game that is still running, or a server that was killed instead of stopped, can leave a chunk half written.

Open the folder for the profile you play. In the Modrinth App, right-click the instance and choose Open folder. In the CurseForge app, right-click the pack and choose Open Folder. In Prism, right-click the instance, then Folder, then .minecraft. In the official launcher, open Installations, hover the profile, and click the folder icon. Fabulously Optimized’s backup page gives the same kind of clicks if that is the pack you run. Our Create instance lives in Modrinth; that is the folder I would copy.

Copy saves. Copy config. If you added a resource pack or a shader, copy those too. Copy options.txt if you care about the keybinds. If the instance has a script folder, such as kubejs, copy that as well. Those files are the pack’s own rules, and an update can overwrite them.

Put the copy outside the instance. Name it with the date and the change you have not made yet. Do not move the only copy and call the move a backup. Do not put the backup inside the folder you are copying. Open the copy and check that the world still contains level.dat, region, and playerdata.

Keep a second copy on another disk if you can. Restoring throws away whatever you did after the copy.

Change the copy

Read the pack’s changelog before you touch the jars. The line that matters is a removed mod, or a note that the update wants a new world. Create 6.0.10 for 1.21.1 is a NeoForge file (Create 6.0.10 release). Aeronautics 1.3.2 needs Sable. A missing Sable is a load failure, not a reason to open the world on another loader. Fabric vs Forge is why you do not “just try” a Fabric jar in this folder.

Forge and NeoForge can show a screen of missing registry entries and ask whether to continue. Continuing strips those entries. Blocks from the missing mod go. Items in chests and inventories go with them. Putting the jar back after that save does not rebuild it. Cancel the screen, or restore the copy you just made.

A performance mod adds no blocks, so the world barely notices. A content mod with no file for the new version means you wait, or you start a new world.

On the copy, replace the mods folder. Do not leave the old jars beside the new ones. Leftover jars are a common crash, and they get blamed on the world. Leave the world folder. Look at config before you accept the new defaults. Your own settings are in the old files.

Opening the world in a newer Minecraft version converts chunks as they come into view. That conversion does not run backwards. The older version will not read it. The copy from before the open is the way back, which is also why you do not open a local copy of a server world in a newer client.

Two launchers pointing at one .minecraft is how you lose a world without meaning to. Set memory and mods in one place — how to allocate RAM.

What you check, and the server

Load the copy. Walk the base. Open a chest. If the pack has machines or a quest book, look at those. Create contraptions are the obvious walk on our pack. If the copy is wrong, the dated original has not moved.

A server uses the same order. Stop it with the stop command or the panel, not a kill. Copy the world and the mods. Update a second copy, and only then repeat the change on the one people play. The client and the server need the same pack. A player who connects with a different list is refused.

The mods you pick yourself are on Best Minecraft mods. The pack we actually play is still Create Aeronautics. The copy is what makes the next update a choice instead of a save you cannot undo.

Related: Minecraft guides, OptiFine vs Sodium, PC builds, Java snapshot news.

Common questions

How do I back up a modded Minecraft world?

Close the game, then copy the saves and config folders from your instance to somewhere safe. Do it before every modpack update.

What happens if I remove a mod from a world?

Blocks and items from that mod disappear when you load and save the world. Keep a backup before removing anything.

Can I go back to an older Minecraft version after updating a world?

Not safely. Newer versions convert the world as it loads, and older versions can't read it, so restore from a backup instead.