Obfuscation map

Obfuscation maps are ProGuard mappings from old (original) names to new (obfuscated) names for classes and class members that have been renamed. They have been exported in the client.json for every snapshot and release available in the Launcher since 19w36a, and the client.json for 1.14.4 has been updated slightly after 19w36a's release to include obfuscation maps as well.

Usage
The obfuscation maps can be used to remap obfuscated stack traces (as in crash reports) to readable stack traces. A tutorial is available.

Dinnerbone and Adrian Östergård have suggested that the obfuscation maps may make modding easier. Searge has implied that the obfuscation maps can replace certain third-party programs such as the Mod Coder Pack.

Third party usages
The obfuscation maps include enough information to deobfuscate Minecraft for decompilation. Third-party programs may exist for this purpose.

According to the License, such decompiled source code is restricted to internal and reference use.

License
Every obfuscation map file starts with a line indicating the license of the maps. "# (c) 2020 Microsoft Corporation. All rights reserved. These mappings are provided 'as-is' and you bear the risk of using them. You may copy and use the mappings for development purposes, but you may not redistribute the mappings complete and unmodified. Microsoft makes no warranties, express or implied, with respect to the mappings provided here. Use and modification of source code for Minecraft: Java Edition is governed by the Minecraft End User License Agreement available at https://account.mojang.com/documents/minecraft_eula."

Trivia

 * Out of all versions published after 19w36a (September 4, 2019), Combat Test 3 is yet the only one published without any obfuscation map.
 * Unlike previous Combat Tests, the version it forked against, 1.14.4, has obfuscation maps released.
 * All consequent Combat Tests have obfuscation maps released, and are based off versions with obfuscation maps released.


 * As of 1.16, versions released in year 2020 still have  in the license notice in the obfuscation map files.
 * In client obfuscation mappings, the very first function listed is called, an easter egg reference to The Game.
 * This function is used to trigger a Java crash after holding the debug key combination for ten seconds.