This, Not That
by thor12022
This, Not That helps a server owner replace blocks and items from a removed mod with blocks and items from another mod, inside worlds that already exist.
What it does
Worlds that have chunks generated with a mod later removed can show missing blocks. This, Not That swaps those missing blocks and items for ones from a different mod, so a world can keep its layout after a mod change without a new world being started. Its replacement pairs match names such as tin ore and tin ingot, while non-matching names like agate and garnet are paired by hand in the config.
The mod runs server-side only, so players join without installing it. It is published for Fabric alone, with a single 1.17.1 file, 0.6.1, dated 2026-03-25 on the beta channel. No required dependency is listed for Fabric. Its source code is public.
Key features
Block and item swapping
Missing blocks and items from a removed mod are replaced with blocks and items from another mod, including block entity contents.
Automatic pair generation
A command attempts to build a replacement config file for a mod by matching names and tags, though the results can vary.
Config-driven replacements
Each mod gets a Mod-Id.json file in the config directory, where replacement pairs can be edited.
Optional preferred mod
A preferred replacement mod can be set to guide which candidate is chosen when several fit.
Compatibility
Latest build for each game version and loader.
Only full game releases are shown. This mod publishes no snapshot builds.
Use cases
Changing a modpack mid-world
A pack owner who removes one tech mod and adopts another can keep existing chunks and machines instead of starting a new world.
Who it’s for: Server owners and modpack authors who need to move a running 1.17.1 world from one mod's blocks and items to another's. Players need nothing installed.
How it compares
Block Replacement MC1.7.10 is a Forge-only, server-side mod for 1.7.10 under the MIT License. Block Swap works on Fabric and Forge for 1.18.2 – 1.20.1, but is client and server and under the GNU Lesser General Public License v3.0 only. Simple Missing Replacer is NeoForge-only for 1.21.1 – 1.21.5, server-side only and under the MIT License. This, Not That is the Fabric option for 1.17.1.
| Mod | Loaders | Game versions | Environment | Updated |
|---|---|---|---|---|
| This, Not That | Fabric | 1.17.1 | Server-side only | 2026-03-25 |
| Block Replacement MC1.7.10 | Forge | 1.7.10 | Server-side only | 2024-02-19 |
| Block Swap | Fabric and Forge | 1.18.2 – 1.20.1 | Client and server | 2023-06-20 |
| Simple Missing Replacer | NeoForge | 1.21.1 – 1.21.5 | Server-side only | 2025-05-03 |
Questions
Which loader does This, Not That need?
Does the server need This, Not That installed?
Where are replacement pairs set?
Does it work on versions other than 1.17.1?
In the catalog
This, Not That is one of 8,515 World generation mods on ModsFinder, and one of 4,027 World generation mods for Fabric. 4,181 mods support Minecraft 1.17.1.
More from thor12022
Similar mods
What the author says
A Minecraft mod to replace blocks and items from a missing mod with different blocks and items. For Mincraft 1.17.1 with the Fabric loader.
Official listing
- Modrinth page
- modrinth.com/mod/this-not-that
- Owner
- thor12022
- Published
- 2026-03-25
- Updated on Modrinth
- 2026-03-25
- Facts verified
- 2026-10-15