In general, all of the Fabric download URLs accept the following GET parameters:

• yarn - Yarn version,
• loader - Fabric Loader version,
• format - Download format (different options per endpoint!).

Example:

  https://fabricmc.net/download/mcupdater?yarn=19w02a.16&loader=0.3.2.93

The result is a .XML file attachable via an <Import> entry to an MCUpdater ServerPack XML. No custom formats are available.

Example:

  https://fabricmc.net/download/multimc?yarn=19w02a.16&loader=0.3.2.93

The default result is a .ZIP file containing an importable MultiMC instance. Alternate formats:

• patchJson - returns a .JSON representing a MultiMC patch for Fabric.

Example:

  https://fabricmc.net/download/vanilla?yarn=19w02a.16&loader=0.3.2.93

The default result is a .ZIP containing a Fabric game profile, which can be extracted to .minecraft/versions. Alternate formats:

• profileJson - returns a .JSON representing a vanilla Fabric profile,
• shimJar - returns a .JAR containing a single file, “version.json”, with the vanilla Fabric profile. This is intended for future SKCraft/Solder support.