Is there a way to turn .mca files into a human readable format? Is there a way to replace all of a certain block or item in a .mca file?

I would like to replace all instances of a modded block with a vanilla block. I plan on updating my Minecraft java modded world into a newer version, but the newer versions of a mod removes some blocks and items.

I would also like to replace items in inventories and storage and biomes too.

I tried opening .mca files in a text editor, but that just gave me a bunch of symbols. Where do I get started? Are those files zipped or something?

  • @ExpertCoder14 I'm not looking for recommendations. I'm looking for a way to modify game files. Would stackoverflow be a better place? Aug 31, 2020 at 2:40
  • @ExpertCoder14 This question is not asking for a tool ("If there isn't, I don't mind doing some programming myself.") , and questions about game file formats are on-topic
    – pppery
    Aug 31, 2020 at 2:45
  • @ExpertCoder14 It's not mod development. .mca are minecraft world save files. mca files are used by the vanilla game though mods can also use them. Aug 31, 2020 at 2:51
  • @PerfectFiasco Right, that makes things more clear. Thanks for editing your question to clarify your intent, so that others don't make the same assumption I did!
    – One 2 Many
    Aug 31, 2020 at 2:53
  • Uhhh... Isn't this a modding question? I'm pretty sure the average player shouldn't know how to programmatically manipulate NBT.
    – aytimothy
    Aug 31, 2020 at 22:39

2 Answers 2


One of the most common tools for editing Minecraft files is NBT Explorer.

It doesn't do what you need, but since you mentioned you can program it yourself here are some pointers:

The .mca file format is called Anvil file format and is based on Region file format with changes to the chunk format. The description in the wiki is not very friendly but basically, to read anvil files:

NBT Explorer is open source, so you'll be able to borrow some code from there, specifically this part seems to be concerned with the actual parsing and interpreting of the data.


If manually going through NBT Data is not your thing, you can use editors such as:

And mass-editing the world in-game instead. There's also the /fill command.

Edit: This may be what you're looking for

  • I'm trying to edit a modded world, but the process should be same for vanilla and modded. For instance, I might want to replace all grass blocks with podzol. At least, I hope it's that way. WorldEdit wouldn't work because I need to do search and replace in all generated chunks. Sep 1, 2020 at 2:33
  • WorldEdit has mod support, don't worry.
    – aytimothy
    Sep 1, 2020 at 2:36
  • I should have been more clear. I also want to replace all of a specified item, whether it's in a player inventory or chests. I don't think WorldEdit can do that. Sep 1, 2020 at 7:40

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