Fabric

Fabric is a lightweight modloader. It has a separate API, required by most but not all Fabric mods in the mods folder. It has been worked on alongside the 1.14 snapshots of Minecraft Java Edition since before snapshot 18w49a (before December 5th 2018). It was created in 2016 as a hobby project of asiekierka.

It is currently supporting 1.14.4 and 1.15.2. It also supports the latest snapshot (20w12a) & combat test (currently combat test 5).

Known installation methods of Fabric
MultiMC was the first launcher (albeit third-party) to support the Fabric Modloader.

As of August 11 2019/0.6.7 update (around this time) MultiMC announced and added in an update to the launcher with an 'Install Fabric' button to allow for easier installation of the modloader compared to its prior zip importing method required before. Forge 1.14 support is not available for the launcher currently due to the current state of the modloader and MultiMC being unable to handle the differences Forge 1.13+ has been changed to, making Fabric the only current way to have mods added for 1.14+ with the launcher and possibly in the future (including snapshots that can be modded). There is currently support for 1.15 release and snapshots support for Fabric, from 19w35a to 1.15.2 Pre-Release 2 (Better citation inclusion needed https://multimc.org/posts/forge-114.html).

The Minecraft Java Edition Launcher was supported not long after 18w50a via the Fabric Installer.



Installation instructions for the Minecraft Java Edition launcher
Fabric Installer is purported to be the tool to make instances of 1.14 Minecraft Java Edition snapshots from Minecraft versions 18w49a and onwards to be modded (public knowledge, but not accurate). Fabric API is a core mod of sorts for mods. It is best to not get these mixed up.

Fabric Installation instructions can be found on the Fabric wiki here.

A step by step process is available below:

Fabric is installed into the Minecraft Java Edition launcher from a tool on the Fabric Wiki [here http://fabric.asie.pl/use/]. This source has two MAIN methods: one for MultiMC and the vanilla Minecraft Java Edition launcher. Since this guide assumes the user will be using the vanilla launcher, select that tab and Click the 'download.jar' button for the Installer. Once it is downloaded, double-click on the file.

There are a few options to be aware of.

Once Fabric has installed its profile (it is recommended to do this the first time Fabric is installed), it will be either installed already or the user will have to select the Fabric version from the Launch Options tab. Fabric snapshots can be switched at any time from the Installations tab to update as well and use the same profile; untick the Create profile check box on the Fabric Installer window to do so and it will not create a profile but will install the updated Fabric loader version desired.

The Fabric API is also needed to make mods possible to run in this instance (not all but many do require it). Fabric API is like a library mod that is required by mods that are in the Fabric environment to work. The common source to get Fabric API builds is from Curseforge.

Once Fabric API is downloaded and placed inside the Mods folder and Fabric Loader is installed for Minecraft Java Edition (along with other mods the player chooses to use) the game will become ready for modded play. Sometimes, when Minecraft snapshot versions bump, Fabric API may need an update as well.

'''Note: Like Rift, or Forge for Minecraft 1.13.2, Fabric does not read mods in individual folders. While Forge might have been able to read folders from 1.12.2 when they were put into it, Fabric cannot.'''

Curseforge source for Fabric API builds can be found here.

Unofficial Twitch Fabric Support Methods Known (Vanilla to Twitch & Jumploader)
More Modloader support for Twitch has been wanted by players and while there is a request (which you can find here: https://twitch.uservoice.com/forums/915910-game-mods-curseforge/suggestions/36229021-more-modloader-support-across-curse-without-being and is a request for support towards Liteloader, Rift & Fabric support besides just Forge) support for Fabric in the Twitch Launcher has been made possible by 2 known unoffical methods. There is also tagging for Rift & Fabric mods on Curseforge.

1.The first unofficial method (dubbed the 'Unofficial Vanilla to Twitch Method') allows users to unofficially get Fabric to work (but you can't export to modpacks, and the profile doesn't stay so features are limited). This was the only support available at the time besides the waiting of Twitch launcher Development teams to implement Fabric into the launcher or Mod Developers to find a way (or without the need to manipulate more than was necessary) to make this possible with the launcher (this method is now outdated, has less benefits and isn't very stable).

2.The second unofficial method gives more functionality and more natural support using a mod, that mod is called Jumploader and it works from 1.14 to even 1.16 snapshots. Both methods will be listed here for those interested.

Vanilla to Twitch Method Tutorial (found out by SuntannedDuck2):
The unofficial method is possible if you have a Vanilla/Minecraft Java Edition launcher with Fabric already installed. If you have the .fabric, .mixin.out and Fabric Loader available in your .minecraft folder then you are ready to use them for this method, the method won't work without these. Now that you have these files/folders, you want to copy the .fabric and .mixin.out folders to the 'Install' folder (on in the folder for that instance you want Fabric to be setup for as it will likely read those files and the mods from there) of your Twitch launcher files. This is to provide the necessary aspects of Fabric available to the game/launcher. Once you have copied them you'll want the Fabric Loader version (snapshot or release both work) that is in your Vanilla instance and to copy it and place it into the 'Versions' folder. This is the profile/version the launcher will use to load the game similar to a Forge or Vanilla setup instance. Now just load up the launcher and you'll see the profile there ready to go, just make sure to have Fabric API and other necessary mods and you ready to play.

Warning: This method is known for the profile not always sticking to the one you selected and reverting back to the previous. Modpacks can also not be exported using this method.

Notice: The Fabric Loader may be the only thing required but it is useful to have the .fabric and .mixin.out folders/files so the game doesn't have to load these for the first time meaning it just has to read the files and continue on.

This method is useful for snapshots when using the Fabric Loader (such as the 1.16 snapshots) but otherwise it is recommended to use Jumploader for better results and release versions from 1.14 to 1.15.

Jumploader Tutorial (mod made possible by Comp500):
Jumploader is a method that is similar to installing a mod in a Fabric environment and allows for natural access to features of the launcher like using Fabric in the Twitch launcher, exporting modpacks, the profile staying still instead of reverting back as examples.

To setup Fabric in Twitch with Jumploader the user will want to download the mod first which can be done so from here: https://www.curseforge.com/minecraft/mc-mods/jumploader, once the user has the mod, they can create a new instance in Twitch or use an existing but it is more recommended to use a newly created for better results due to how Jumploader works. When creating a new instance in Twitch it will be important to consider the game version (1.14 to 1.15, 1.16 can be tricky to setup when using Forge and selecting profiles for new instances) and the Forge Modloader dropdown box. Jumploader considers Forge and allows Fabric mods to work, it does not allow Forge and Fabric mods to work alongside each other. So if you have Forge mods in an existing instance they will likely be ignored. Using Jumploader without a Forge Modloader version selected might work but it is best to try this having not considered the above "Unofficial Method's" Fabric Loader consideration.

Once the user has Jumploader (and Fabric API if needed) in the mods folder, a Forge Modloader version selected and other Fabric mods (works for release versions, the same cannot be said for snapshots as Forge isn't available for those, if you want snapshots to work it is best to just have a Fabric Loader version for snapshots and ignore the Forge Modloader versions when the instance was created) the game should load up successfully with the Fabric mods enabled.

Modpack Support:
Modpack exporting is also the same as if the user were to export a Forge modpack, the only conflicts that should happen are mods that are causing conflicts.

Mod Menu Notice:
If you're new to Rift or Fabric you'll notice there is no 'Mod Options' button like with Forge. This is due to the option not being built into the modloaders/Fabric API, it is instead a separate mod, this is due to keeping things lightweight as well as for specific limitations if it were bundled. Also players could consider it optional (similar to Fabric API where it is used for some mods but not all in terms of how optional it is) if they aren't interested in knowing how many (or what in particular) mods are installed, or tweaking configs (if the mod developer has configs and has made it accessible through Mod Menu). You can download Mod Menu to take advantage of these benefits here.

MultiMC Fabric Installation Tutorial 1.14.4 tutorial instructions
There is two known ways to install Fabric for MultiMC. The "Fabric Install Button" and "Importing From Zip" methods.

The Fabric Install Button method is as simple as creating a new 1.14+ instance on MultiMC, then editing the instance to install Fabric how you would Forge or Liteloader for 1.12.2 and prior. By installing Fabric you are installing the Fabric Loader and Intermediary Mappings. Once this is installed just put your mods (including Fabric API) and it should load up correctly stating Fabric after the Minecraft version such as "Minecraft 1.14.4/Fabric."

The Importing from Zip method. requires you to go to Fabric's website here: https://fabricmc.net/use/ and selecting the correct loader version and Game/Mappings version, once you have selected the versions from the dropdown box you have two buttons to choose from, Download MultiMC Instance or Copy MultiMC Instance URL. The Download instance button will give you a zip file you can download to your local hard drive and import with MultiMC, while the Copy URL button copies the URL to your clipboard. Both need you to put a link of either the URL or the zip file folder location to set it up this way. Once the instance is created, just add the mods (including Fabric API) and it should be good to go.

Vanilla instructions
Once a modded Fabric setup has been made, download [Optifine https://www.optifine.net/downloads], go to the downloads, and select from the preview versions and put the Optifine preview file into the mods folder alongside OptiFabric which you can be downloaded from [here https://minecraft.curseforge.com/projects/optifabric] to use for compatibility between the two. One thing to consider with the OptiFabric installation is that the preview file can be used as is (out of the box) or extracted to get the same result; this is not the case with other modloader installations as far as it is known when it comes to OptiForge or OptiRift, but without OptiFabric it will not work with a Fabric created instance; this applies to both the Preview file and the extracted method. This is unrelated to the Optifine install for vanilla 1.14.2 and only applies to Fabric modded instances for 1.14 versions. Once it is loaded up Fabric mods will work alongside Optifine.