Surrogate

IMPORTANT: This is not a replacement for regular backups. It is intended for use by mod and modpack developers.

Normally, Minecraft will respond to missing blocks/items by replacing them with “air”, meaning your test world is corrupted if you accidently removed modded blocks or items.

 This mod detects missing blocks (including block/tile entities) or items in your save file and replaces them in game with a surrogate holding all the original data.

 When these surrogate blocks/items are saved, the data is written back into the save file exactly as it was read.
So you can fix the problem with the missing/broken mods and recover the data by reloading.

Documentation for additional information.

Distribution is allowed as long as you comply with the LGPL and Minecraft’s EULA.

This mod is for Fabric. Forge has a different mechanism, see the documentation for an explanation.