I'm trying to get started modding Minecraft. I opened up the minecraft.jar file in Eclipse, but it doesn't contain what I expected.

In this tutorial the presenter decompiles minecraft.jar and finds things like armor and blocks packages, but when I put my minecraft.jar file (from [user]\appdata\roaming\.minecraft) into Eclipse, I only see Apache and Ydggrassil authentication and such.

What am I doing wrong?

  • \$\begingroup\$ This question should be closed as an attempt at a breach of copywrite. \$\endgroup\$
    – War
    Aug 10, 2014 at 18:00
  • 3
    \$\begingroup\$ This topic is perfectly acceptable here, but I am not really sure this is a good question for this site. \$\endgroup\$
    – user1430
    Aug 10, 2014 at 18:08
  • 1
    \$\begingroup\$ fair enough, someone pointed out that EULA allows this (wierd but cool) :) \$\endgroup\$
    – War
    Aug 10, 2014 at 18:10
  • 3
    \$\begingroup\$ Why is this not a good question for this site? \$\endgroup\$
    – vroomvsr
    Aug 10, 2014 at 18:29
  • 7
    \$\begingroup\$ @Wardy Just to seal it with a reference: Here's the EULA. It says "If you've bought the Game, you may play around with it and modify it." \$\endgroup\$
    – Anko
    Aug 12, 2014 at 15:18

1 Answer 1


You can't just open the jar in Eclipse. Even if you have some kind of decompiler-plugin, you will only see obfuscated code.

You will need the Minecraft Coder Pack to decompile and deobfuscate the jar (as well as MCP can anyway) so you can work with the code.

Additionally, if you want do develop Minecraft-Forge mods you should check out this page. Forge also requires MCP to decompile the jar, but it's automatically downloaded during installation.

  • \$\begingroup\$ If I remember correctly, nowadays Minecraft also ships with a dictionary of what got obfuscated to what, officially. \$\endgroup\$ Jun 16, 2021 at 8:40

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