Litematica version editor
Rewrite the version fields so an older Minecraft can open the file. The editing happens in your browser. The file is not uploaded.
How it works
An older Litematica rejects a newer .litematic for one reason only: a format check saying Version is above its ceiling. Lower that and it loads.
The DataFixer only runs when MinecraftDataVersion is older than the game. Otherwise nothing is converted, and blocks are looked up by name as written.
Any block that version does not have becomes air. Properties that version does not have are dropped and take their default (this is vanilla NbtUtils.readBlockState). Blocks whose name and properties are unchanged read as they were.
Leave MinecraftDataVersion at its original value. Set it below the game you open it in and the DataFixer runs, applying old-to-new fixes to data that is already new and breaking it.