Minecraft what belongs to which mod?

Is there a way to show me in the game which mod an item, NPC or building belongs to?

Depends on.

If you play with a ready-made modpack, there's usually a mod called NEI or JEI (Not Enough Items or JustEnoughItems). With that you can then filter for certain items by name, ID or mod.

Name → example item

ID → #XXXX

Mod → @Example Mod

Mod Name Tooltip shows you which item and which block belongs to which mod.

https://www.curseforge.com/...me-tooltip