.BO4 File Extension

Minecraft Java Edition players can install the OpenTerrainGenerator plug-in and use it to create and load custom Minecraft worlds. Each OpenTerrainGenerator world is generated using one or more biome configuration (.BC) files. In turn, each biome configuration file references a set of BO4 files, which contain information about custom structures that appear in the biome.

BO4 files are created in-game using the /otg export StructureName -bo4 command. The referenced structure is then exported as two or more BO4 files. The first BO4 file, named StructureName.bo4, contains settings that apply to the entire structure and define placement, distribution, and blending with terrain. Each subsequent BO4 file contains information about an up-to-16x16 block section of the exported structure. When creating a custom world, modders place BO4 files in the world's WorldObjects directory.

NOTE: You can convert .SCHEMATIC files to BO4 files using OTGEdit.

You can open and edit a BO4 file in any text or source code editor, such as Microsoft Visual Studio Code (cross-platform). Keep in mind that editing a BO4 file may break the custom structure the BO4 file defines.