minecraft-launcher/utils/assets-downloader

About assets

The game itself downloads (through the launcher) further resources from

https://resources.download.minecraft.net/

⚠️ http://resources.download.minecraft.net/ no longer works - you must use https

The asset index for each version is linked in the <version>.json. An example url to the asset index could look like this

https://launchermeta.mojang.com/mc/assets/1.12/67e29e024e664064c1f04c728604f83c24cbc218/1.12.json

Each resource in the file has a name (the field name of the resource object), a SHA1 hash, and a file size. The client currently downloads all resources in the index from

https://resources.download.minecraft.net/<first 2 hex letters of hash>/<whole hash>

and stores them in

.minecraft/assets/objects/<first 2 hex letters of hash>/<whole hash>

and a copy is stored in

.minecraft/assets/virtual/legacy/ 

in the old format for versions that don't support the new system (1.7 and below)

ℹ️ From: https://wiki.vg/Game_files#Assets