Minecraft Java world map editor — view your save, edit chunks, build in 3D
Open a Java save from .minecraft/saves and explore it in the browser: a 2D top-down map, 3D edit mode with WorldEdit-style stamps, chunk biome changes, spawn and gamerules. Export the whole world or just the .mca you changed. Latest Java (1.21 / 26.x) — nothing leaves your machine.
Drop a world zip, folder, or region files
Zip or drop the world folder from .minecraft/saves, or just drop one or two r.X.Z.mca files from region/. Use a real .zip — 7-Zip’s default .7z will not open. Nothing is uploaded. Latest Java only (1.21 / 26.x).
What this tool does
It indexes your world zip or folder, reads level.dat, and only inflates the .mca region files for the area on screen. The 2D map is a top-down view of the highest solid block, tinted by biome — so you can see plains, desert, ocean, and Nether biomes before you change them. Click a chunk to set its biome, fill it with a block, or clear it. World settings write back to level.dat. Chunk and biome edits write the region file you can overwrite in saves.
How to change a chunk biome
People usually want this for an existing world: turn a plains spawn into cherry grove, fix a desert village that generated in the wrong biome, or paint ocean over a river. Click the chunk on the map, pick a biome (or type an id like minecraft:pale_garden), then Set chunk biome. That writes the 1.18+ biome palette on every section in the chunk — the same data /fillbiome edits, but for the whole chunk at once. Grass, foliage, water, sky, and mob spawning follow the new biome. Trees, dirt, and buildings already there stay put. Export the .mca and drop it into a copy of the world (26.x: dimensions/minecraft/overworld/region/).
What you can edit
- One or two region files — drop r.X.Z.mca from region/ if you do not want to zip the whole world.
- Change a chunk biome — plains, desert, cherry grove, pale garden, mushroom fields, lush caves, sulfur caves, Nether biomes, or any id you type.
- Chunk terrain — fill a selected chunk with stone, water, air, or another block, then download that r.X.Z.mca.
- World settings — spawn, hardcore, cheats, difficulty, game mode, day time, rain, thunder, and the world border.
- Gamerules — keepInventory, mobGriefing, doDaylightCycle, randomTickSpeed, spawn radius, and more.
- 3D edit mode — WorldEdit-style stamps (floor, wall, room, sphere, dome, tower, pyramid), then export the changed .mca files.
- Structures — paste a structure-block .nbt or Sponge .schem onto loaded terrain in the 3D view.
How to use it
- Close the world in Minecraft, then open the saves folder (.minecraft/saves on Java).
- Right-click the world folder and compress it to a .zip (Windows: Send to → Compressed folder; Mac: Compress) — or drop the folder, or just the r.X.Z.mca files you care about.
- Drop that zip or folder here. If you included more than one world, pick it from the list.
- Pan and zoom the map. Click a chunk, pick a biome, and hit Set chunk biome — or fill blocks, or open 3D edit mode.
- Export everything, or just the .mca region file for the chunk you edited, and overwrite those files in a copy of the world folder.
Limits
- Java Edition only. Bedrock uses a different save format.
- Built for latest Java (1.21 / 26.x) Anvil chunks. Older worlds are not a support target.
- 3D edit mode paints on loaded chunks (surface and stacked blocks). Ungenerated chunks cannot be written.
- Huge Zip64 archives (zipping every save at once) may fail. Zip one world folder if that happens.
- Always load the edited files in a backup world first.
FAQ
- How do I zip my world?
- Open .minecraft/saves, right-click the world folder (the one with level.dat inside), and compress it to a zip. Upload that file — or drop the folder itself. You do not need to pick files out by hand.
- Can I upload just one region file?
- Yes. Choose or drop r.X.Z.mca from the world’s region folder (or DIM-1/region, DIM1/region). You can pick several. World settings need a full save with level.dat; region-only sessions export the edited .mca files.
- How do I change the biome of an existing Minecraft world?
- Zip or drop the world folder from .minecraft/saves, click the chunk on the map, pick a biome, then Set chunk biome. Export that r.X.Z.mca and put it back in a copy of the world. 26.x uses dimensions/minecraft/overworld/region/ (Nether: the_nether, End: the_end). Older layouts use region/, DIM-1/region, or DIM1/region.
- Can I change a chunk biome?
- Yes. Click the chunk, pick plains, desert, cherry grove, pale garden, or type any biome id, then Set chunk biome. The map grass and water tint update right away. Export the region file to use it in-game.
- Is this the same as /fillbiome?
- Same idea, different shape. /fillbiome paints a box at 4×4×4 biome resolution. This tool sets the whole selected chunk (all sections) to one biome, which is what most people want when they search “change chunk biome”.
- Will trees and villages change when I change the biome?
- No. Already-generated blocks stay. Grass color, water color, rain/snow, and new mob spawns follow the new biome. To replace the terrain itself, fill the chunk or paint in 3D edit mode.
- Does my world upload to CraftMC?
- No. The zip is read in your browser. Region files are inflated only when they appear on screen.
- Can I edit every block like MCEdit?
- You can paint and erase blocks in 3D edit mode on generated chunks, fill a whole chunk from the 2D map, or paste a structure. Export the changed .mca files. It is not a full underground world editor.
- Will this work on last year’s Java?
- The parser expects current Java chunk NBT (1.21 / 26.x). Older worlds might draw, but we are not supporting those formats.
- What do I replace in the world folder?
- If you only changed a chunk, download that region’s r.X.Z.mca and replace the same file. 26.x worlds use dimensions/minecraft/overworld/region/ (the_nether / the_end). Older worlds use region/, DIM-1/region, or DIM1/region. For spawn or gamerules, download level.dat or use Export everything.