Obfuscation map

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This feature is exclusive to Java Edition.

Obfuscation maps are ProGuard mappings from old (original) names to new (obfuscated) names for classes and class members that have been renamed.[1] 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.[2]


The obfuscation maps can be used to remap obfuscated stack traces (as in crash reports) to readable stack traces.[3] A tutorial is available.

Dinnerbone and Adrian Östergård have suggested that the obfuscation maps may make modding easier.[4][5] Searge has implied that the obfuscation maps can replace certain third-party programs such as the Mod Coder Pack.[6]

On August 12th, 2020, Dinnerbone states that modding projects can switch to official Mojang names provided in the obfuscation maps.[7]

Third party usages[edit]

The contents of this section are not supported by Mojang Studios or the Minecraft Wiki.

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.


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.

Per Dinnerbone, any obfuscation mapping released before the license update would be still available under this older license in addition to being available under the new license.[8]


September 3, 2019Dinnerbone mentions "a small surprise for modders!" for 19w36a.
Java Edition
1.1519w36aDownloads to client and server obfuscation maps are now included in client.json.
September 4, 2019Dinnerbone releases obfuscation mappings for 1.14.4 as well.
August 12, 2020Dinnerbone indicates the license of the obfuscation maps will be updated and encourages modders to switch to Mojang's obfuscation map, claiming in another tweet that it would "help with compatibility".
He offered a preview of the updated license as well.
August 14, 2020The license of obfuscation maps was updated.
The version_manifest.json was updated to have client.json entries for 1.14.4 and versions since 19w36a to link to updated obfuscation maps.


  • 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.
  • Before the August 16th, 2020 license update, versions released in year 2020 had # (c) 2019 Microsoft Corporation. in the license notice in the obfuscation map files.
  • Despite that Combat Test 8b is published after the license update, it still uses the old license notice and has the 2019 year notice.
  • In client obfuscation mappings, the very first function listed is called youJustLostTheGame(), an easter egg reference to The Game.
  • This function is used to trigger a Java crash after holding the debug key combination Ctrl+F3+C for ten seconds.