Litematica vs WorldEdit vs Schematica

Three tools get called "the schematic mod", and they do different jobs. Which one you want depends on whether you are pasting instantly or rebuilding by hand, and on which file format you have.

Litematica

A client-side Fabric mod. It shows a build as a ghost overlay and you place the blocks yourself — or let Easy Place do it in creative. Because it is client-side it works on any server you can join, including ones where you have no permissions at all. It reads .litematic, .schem, .schematic and .nbt, which makes it the most forgiving of the three.

WorldEdit

A server-side plugin (or single-player mod). It pastes a build instantly with //paste, which is the fastest way to put a schematic down — but you need WorldEdit installed and permission to use it, so it is a server-owner tool. It reads .schem (the modern Sponge format) and the old .schematic, and it does not read .litematic.

Schematica

The original ghost-overlay mod, for Forge and for old Minecraft versions. It reads .schematic only. It is effectively frozen — if you are on a modern version, Litematica replaced it.

Picking one

If you only want to look at a build without installing anything, the 3D editor on this site opens all four formats in the browser.