This, Not That: Replace Missing Mod Blocks in Minecraft
Few things sting like loading an old world and finding holes where your favorite tech mod used to be. You swapped AnnoyingTechMod for FunTechMod, but your terrain still generates tin ore that no longer exists. Starting over is painful, and WorldEdit on a large world can choke for hours. This, Not That for Minecraft solves that exact problem by replacing blocks and items from missing mods as your world loads, so the update happens while you play.
What This, Not That Does
This, Not That is a Minecraft mod that swaps blocks and items from an absent mod with different blocks and items from a mod you actually have installed. The replacement runs when a chunk loads, which means you do not need to regenerate terrain or travel to fresh chunks to find the world gen you need. If your pack once used annoying_tech:tin_ore and now uses fun_tech:tin_ore, you simply pair those two names in a config file and the mod handles the rest.
You are not limited to similar items either. If AnnoyingTechMod had annoying_tech:agate but FunTechMod offers fun_tech:garnet, that pairing works just as well. The mod is built for Minecraft 1.17.1 with the Fabric loader, so make sure your instance matches before you begin.
How to Install This, Not That
Requirements
- Minecraft 1.17.1 with the Fabric loader installed
- Fabric API
- A backup of the world you plan to load
Installation Steps
- Place the This, Not That jar file into your mods folder.
- Launch the game once so the config directory is created.
- Add your replacement pairs to the generated config file.
- Load your world and watch chunks update as they load.
If you would rather skip the manual setup, the foxygame.net launcher makes short work of it: This, Not That sits in a browsable add-on catalog, so you can install it in one click and let the launcher keep it updated and matched to your game version automatically.
Generating a Replacement Config Automatically
Writing hundreds of pairs by hand is tedious, so This, Not That ships with a command that builds a starter config for you. Run /this_not_that generate <Mod-Id> [Preferred-Replacement-Mod-Id] with the mod you want to replace installed. The mod writes a file named this_not_that.<Mod-Id>.json into your config directory, matching replacements by the closest tags and names it can find. The optional preferred mod parameter is a hint, not a guarantee.
Treat the output as a best guess. It performs well for technical items like ores, dusts, ingots, nuggets, and tools, but decorative blocks may get odd matches. Modpacks that rewrite tags for unification can also interfere, so verify the results before loading a world you care about.
Rules and Limitations to Know
- Cannot replace anything that still exists in an installed mod or in vanilla.
- Only replaces things with the default version of that item.
- Cannot replace in-world BlockEntities, though the item form usually works.
- Searches vanilla chests, barrels, hoppers, and similar storage, with mixed results for modded containers.
- Damage transfers proportionally, custom names carry over, and only valid enchantments are kept.
- Replacing ItemBlocks of specified blocks and items in player inventories and Ender Chests are both config options.
A block replacement will not work for something like annoying_tech:nuclear_furnace, but an item replacement will. Large replacement lists can cause a noticeable hitch when chunks load, so keep your pairs tight. Always back up your world first and scout the area before committing to a long play session.
Final Thoughts
This, Not That turns one of modded Minecraft's most annoying headaches into a config file and a single command. Rather than abandoning a world or praying for a WorldEdit miracle, you get a clean path to swap ores, tools, and loot on the fly. Download This, Not That, generate your config, back up your save, and your old world can live on under a new mod list.