1.21.1 Porting Guide

This guide by getplayerhead.sh?eevee_27&16.png eevee_27 is written for players who want instructions on upgrading your Minecraft Java client to 1.21.1 on your computer before MinecraftOnline completes its upgrade.

Disclaimers

THIS PROCESS CANNOT BE UNDONE. Minecraft has (nearly) entirely changed within the 9 years of game development. While some data can be converted or transferred from one to another, some data cannot. Once the upgrade/porting is done, the converted data cannot be reverted. Backing up files is heavily recommended.
Minecraft 1.21 is a wide, huge release version. Almost every patch is a major release; ONLY use contents supported for `1.21.1`.
This tutorial contains steps for installing Fabric mods. If you are unfamiliar with the concept of "modding", consider creating a new directory (folder) and using third-party launchers by following Step B of this guide.
If you are currently using 1.16.5, 1.19.2 or other ViaFabric(+) clients, you will need to empty the mods folder first and then go through the guide. Skip steps for installing Fabric Installer.
- This assumes you are not using ViaBackwards or the alike. Proxy is unnecessary.

Walkthrough

Before starting

BACK UP YOUR MINECRAFT FILES. Proceed at your own risk.
Choose between A: continuing to use the current Minecraft directory (folder) and update everything within, or B: create a brand new directory and add files into it (recommended).
- Step A will use the vanilla launcher, and Step B will use Prism Launcher.

Getting Started

1. Update your Operating System to the latest supported build. What if you cannot? Why would I know? Perhaps buy a new computer, I dunno.
2. Install Java 21. Java 21 is supported and necessary for Minecraft 1.21 versions. If it is not preinstalled on your computer, download it from Oracle [1]. Once the installation is complete, you may need to restart your computer.

Why is Java 21 necessary? Java is the core program used in many applications nowadays, and Minecraft runs on it. In older versions of the game, such as 1.12.2, Java 8 was the main supported version. This has changed as the game has modernised, and Minecraft 1.21 supports Java 21, the latest long-term support release of the Java platform. Do note that if you wish to continue playing older versions of the game (or other older apps in general), you should not uninstall Java 8 and/or other older versions.

Update

Step A Users

Step A users will use the vanilla launcher to update the game, then install Fabric mods on the currently in-use directory.

1. Open Minecraft Launcher. From the Minecraft Java Edition top, click Installations and hover over your mouse on the current profile on which you use to play on MCO. Click the ‣‣‣ -> Edit button that appears.
2. On the profile settings, change the Version to Release 1.21.1. Optionally, change the profile name and icon for accessibility.
- If you experience lagspike when playing the game and have spare RAM memory to use on your computer, this is a fine time to change the allocated memory for the game. Under the More Options menu, there is a text field for JVM arguments with text “-Xmx2G ...”. Change the number there to the number of gigabytes of RAM that you want to allocate to the game.
  - This number should be under 50% of your total RAM. Recommended is 25% of RAM - for instance, 2GB if you have 8GB in total, 4GB if you have 16GB in total.
  - You cannot use decimal numbers in this field - otherwise, Java will throw up and crash upon game startup.
  - Keep in mind that if your computer’s RAM usage goes to 100%, the system can throw up and crash.
3. Save profile settings, and hover over the profile again to hit Play. If you have never played on 1.21.1, the launcher will promptly install it.
- Do not fret if you have mods in your directory! As the game is using a “vanilla” version of the game, the mods folder will be ignored. You can empty this later.
- With this step, vanilla setting files are overwritten. Most settings, controls used for your mods, texture packs or resource packs are reset. Any vanilla controls from 1.12.2 are not changed. You may check these once the game loads.
4. Once the game loads, click Singleplayer and open a world. This can be new or old.
- If you have any worlds that you would like to update from older versions, including 1.12, you may use them; however, worlds from before 1.18 require world conversion. By doing this, worlds will not be safe to be loaded from any prior versions.
5. Once the world is loaded, leave the world, quit the game and close the launcher.
6. Now use the browser to access the Fabric homepage [2]. From there, download the Fabric Installer file.
7. Open the Fabric Installer. If prompted, allow access to your computer.
8. In the Fabric Installer, select Minecraft Version 1.21.1 and the current Minecraft directory on your drive in Launcher Location. Don't forget to untick the box in "Create profile." Hit Install when ready, and the installer will do its job.
- Fabric build should be auto-selected to the latest build for the game version.
9. When the installation is complete and the prompt appears, click the link for Fabric API. Keep the tab on the browser open for now. Click Done on the dialogue and close the installer.
10. Now open the launcher and head over to the Installations tab. Hover over the profile you edited previously, and click Edit.
11. Change the selected version to the latest Fabric Loader build for 1.21.1 that you have just installed.
- Note that, depending on build numbers, name formatting may be different. Always check for build numbers.
12. Save profile, and now, hover over the profile again to select the folder icon. This button will open the directory folder in the file explorer. Open the mods folder within and keep the explorer window open.
- If the mods folder is not in place, simply create a folder in the Minecraft directory.
- Before heading to the next step, you should empty your mods folder. If you need them to remember the name of mods, drag them out of the folder to places like the desktop.
13. Head back to the browser, and download Fabric API on CurseForge [3] and ViaFabricPlus on Modrinth [4]. If needed, you may download other mods at this time.
- For the list of required and recommended mods, jump to CHAPTER.
- IMPORTANT: It is within YOUR RESPONSIBILITY to be sure that the mods you are downloading are safe to use without risks of cheating. If there is, turn off all the modules that count, and if not possible, delete those mods from your folder. You should test all the mods' functionalities in a singleplayer world before using them in a multiplayer server.
14. Move the mod files into the mods folder.
15. In the resourcepacks folder, add packs.
- For the list of recommended resource packs, jump to CHAPTER.
16. Hit Play with the modded Fabric 1.21.1 version.
- IMPORTANT: If there are issues with the modification to your directory (such as unsupported version for mods or mod conflicts), Fabric Loader will create a crash report for you. Follow the instructions in it to start up Minecraft without an issue.
- On Windows, the OS may pop up a warning regarding connection to the Java runtime (Minecraft). You must allow it to connect to any services in-game.

If Minecraft launches without any crashes, you are almost complete! Be sure to check the mods that you have installed, and adjust settings to abide by the server rules. Once complete, jump to #Connect.

Step B Users

Step B users will use a third-party launcher for Minecraft - Prism Launcher. If you do not have it, download and install it from here. You can keep the settings as the default.

What is Prism Launcher? This is an open-source launcher for Minecraft forked off of MultiMC, a different third-party launcher. Whilst keeping simplicity, it can do advanced setups and is somewhat commonly used in the modding community.

1. Once Prism Launcher is installed, open the launcher. You may be asked to log in to your Microsoft account, so login with the account that is linked to your Minecraft account. You can access the account manager from the button on the top-right.
2. On the launcher, click Add Instance.
3. On the new window, type in the name, choose an icon for the instance, (optionally) assign a group name for the instance, and select the game version and the mod loader.
- By default, the window will open on the Custom tab. Scroll down to select 1.21.1 for the version, and select Fabric for the Mod Loader. You should use the latest build of Fabric unless specified by some mods.
4. Click OK, and the instance will be created. Click on the new instance once, and from the menu on the right, click Edit. This is where you can adjust all the settings for the instance.
5. Click the Mods tab and add mods from there. Mods released on CurseForge and Modrinth can be directly installed to Prism from the Download mods button. Otherwise, download mod files from each site and drag-and-drop files to the console window.
- For the list of required and recommended mods, jump to CHAPTER. Make sure to download Fabric API and ViaFabricPlus in this step.
- Because of how some mods are configured, mods may be detected to be used for 1.21. Mods with this issue will be unable to be checked for updates on Prism unless the mod developers fix the issue.
- IMPORTANT: It is within YOUR RESPONSIBILITY to be sure that the mods you are downloading are safe to use without risks of cheating. If there is, turn off all the modules that count, and if not possible, delete those mods from your folder. You should test all the mods' functionalities in a singleplayer world before using them in a multiplayer server.
6. From the Resource packs tab, add resource packs.
- For the list of recommended resource packs, jump to CHAPTER.
7. When ready, click Launch. Prism will automatically download the game files as it launches.
- IMPORTANT: If there are issues with the modification to your directory (such as unsupported version for mods or mod conflicts), Fabric Loader will create a crash report for you, or Prism will open the console window with the game log. Check the possible resolution in the report to launch Minecraft without an issue.
- On Windows, the OS may pop up a warning regarding connection to the Java runtime (Minecraft). You must allow it to connect to any services in-game.

If you experience lagspike when playing the game and have spare RAM memory to use on your computer, you can adjust the amount of RAM allocated in Settings -> Java -> Memory. Click the box to tick and enable the setting.

This number should be under 50% of your total RAM. Recommended is 25% of RAM - for instance, 2048MiB (2GB) if you have 8GB in total, 4096MiB (4GB) if you have 16GB in total.
Keep in mind that if your computer’s RAM usage goes to 100%, the system can throw up and crash.

If you have issues with Prism failing to start the game before the mods folder loads, you may need to edit Java settings.

From the console window, go to Settings -> Java -> Java installation, and tick the box to change the setting.
Click Auto-detect to search for any Java installations on your computer.
Select a Java 21 installation.
If the issue persists, or you do not know what to do, go to Global Settings, and on Java -> General, tick the box "Auto-detect Java version" and "Auto-download Mojang Java". Untick the Java installation setting on the instance settings.

8. Now it is time to transfer files to the new directory. Unfortunately, you must do this process manually.
- For the list of files or folders that can be transferred, refer to CHAPTER.

Connect

Both Step A and B users should follow these steps after the modded Minecraft instance launches and settings have been modified.

1. Go to Multiplayer. Add MinecraftOnline to the server list as you had done before.
2. Before clicking Done, click the ViaFabricPlus button on the top-right corner of the window.
3. A list of supported versions by the mod will show up. Select either "Auto-detect" or "1.12.2".
- In some cases, choosing Auto-detect may not work as intended, as the server would reject the connection for using an invalid version. As such, selecting a specific version is recommended.
4. Once chosen, you will return to the previous screen. Now hit Done to add MCO to the server list.
5. Select MCO and join.

Welcome to MinecraftOnline with a fresh, modern look! Some may feel disgusted with the new textures, but you will have to get along with them.

Useful stuff

What files can be transferred?

Anything not listed here ain't worth transferring.

Files
Folder	Transfer?	Comment
/mods	No
/saves	Yes	Worlds from pre-1.18 requires conversion.
/resourcepacks	No	Pack format has been changed. You cannot use any resource packs from 1.12 in post-Flattening versions of the game.
/shaderpacks	Depends	Depends on the algorithm of the shaders - not recommended to continue using packs made for older versions of the game.
/screenshots	Yes
/schematics	No	Due to the Flattening, any .schem or .schematic files cannot be loaded in correctly. Consider printing all the schematics using Schematica in 1.12.2 worlds and then saving them separately in 1.21.1 using Litematica.
/xaero	Yes	When loaded in newer versions of the game, Xaero's mods will convert loaded in data automatically. You can start full conversion from Xaero's World Map settings.
Settings	Depends	Some settings will be transferred to the new version, while some others will be reset. You may move the following: <.minecraft>/config, options.txt, servers.dat

Recommended mods

Note: It is within YOUR RESPONSIBILITY to be sure that the mods you are downloading are safe to use without risks of cheating. If there is, turn off all the modules that count, and if not possible, delete those mods from your folder. You should test all the mods' functionalities in a singleplayer world before using them in a multiplayer server.

List of recommended mods
Mod name	Download from	Dependencies	Conflicts	Comments
Fabric API	CurseForge	-	-	Core mod for various Fabric mods
ViaFabricPlus	Modrinth & GitHub	-	ViaFabric	Allows connecting to prior versions of the game. Java 1.21.1 support ended on v3.4.9. ViaFabric is not recommended, as it is known to cause various issues. ViaFabric(Plus) on other versions of Minecraft may cause chunk loading issues with custom containers in MCO. This is not reported by players to be an issue in 1.21 versions so far.
GPUTape	Modrinth	Fabric API	Video Tape	GPU optimisation for OpenGL 4.0+
Sodium	Modrinth	-	Optifine	Powerful optimisation mod for modern Minecraft clients. Intended to be a replacement for Optifine. OptiFabric is NOT RECOMMENDED and unsupported for 1.21. [5]
Iris	Modrinth / Website	Sodium	-	Open-source shaders mod
Sodium Extra	Modrinth	Sodium	-	Adds extra features not included in Sodium
Mod Menu	Modrinth	Fabric API, Placeholder API	-	Essential mod to add mod menu for Fabric clients
LambDynamicLights	Modrinth	Fabric API	RyoamicLights, Sodium Dynamic Lights	Fabric and modern version fork of Optifine's dynamic lights function
MacroKeybinds	Modrinth	-	-	Simple keybinds mod
Stendhal	Modrinth	Fabric API	FixBookGUI	Adds additional on-screen GUI to parse extra characters into books, signs, anvils and chat interface WARNING: Use the mod built for 1.21 to use it in 1.21.1.
WorldEdit	CurseForge	-	-	Utility mod making large-scale modification easier WorldEdit CUI is unfortunately unavailable beyond 1.12 and is not included within WorldEdit. This means that you cannot use the Craftbook Debug Stick in a 1.21.1 client.
Litematica	Modrinth	MaLiLib	-	Modern version fork of Schematica WARNING: Using the Save function is considered cheating! Some functions in Schematica are omitted from Litematica or featured on other mods.
MiniHUD	Modrinth	MaLiLib	-	Utility mod to display metadata on-screen, plus additional gameplay support features. WARNING: Includes modules considered cheating! Use default settings to avoid trouble. WARNING: Ping and Server TPS information are calculated on the client-side, and DO NOT COLLECT NOR SHOW REAL VALUES.
AntiGhost 1.20+ Fabric fork	Modrinth	-	-	Scans for "ghost" blocks and pops them back into existence client-side
AppleSkin	Modrinth	Fabric API	-	Adds hunger, saturation and health boost info to the inventory HUD
3D Skin Layers	Modrinth / GitHub	Fabric API	-	Makes armour layer of players' skins 3D Features will automatically be disabled depending on the game's performance.
Distant Horizons	Modrinth	-	-	Visually adds simplified terrain beyond Minecraft's render distance In edge cases where you use the client across multiple servers and do not want to change render distance every time, or have trouble loading chunks by DH, consider using Farsight in addition to the mod.
Presence Footsteps	Modrinth	Fabric API, Kirin (embedded)	-	Adds various footstep sounds in addition to vanilla sound effects
AmbientSounds	Modrinth	Fabric API, CreativeCore	-	Adds ambience sound effects. Compatible with select mods that add custom biomes.
Essentials	Modrinth / website	-	-	Adds tons of cosmetics for players to use. Host singleplayer worlds to play with friends, integrate gameplay status to Discord with Rich Presence, and send screenshots directly in-game. If you use multiple accounts, this mod makes it extremely easier to switch accounts - can be helpful in timeout situations.
Xaero's World Map	Chocolate Minecraft	-	-	Map out your very own world map For minimap features, download the minimap mod alongside. Minimap and Better PVP mods include modules considered cheating, and fairplay versions are strongly recommended. For more information, see Minimap Waypoints.
JourneyMap	CurseForge	-	-	Map out your very own world map JourneyMap is an all-in-one mapping mod, unlike Xaero's mods. WARNING: Includes modules considered cheating! Do not use if you do not understand everything written in Minimap Waypoints.

Recommended resource packs

Note: It is within YOUR RESPONSIBILITY to be sure that the resource packs you are downloading are safe to use without risks of cheating. If there is, turn off all the modules that count, and if not possible, delete those packs from your folder. You should test all the packs' functionalities in a singleplayer world before using them in a multiplayer server.

Recommended resource packs
Pack name	Download from	Dependencies	Comments
ModernisedOnlinePack	this wiki article	CIT Resewn, Continuity, Entity Texture Features, Entity Model Features	1.21 fork of MinecraftOnline Resource Pack by Crafter_Keegan
MCO 3D pack	User:Gnawmon	CIT Resewn +α	Made by Gnawmon. Makes some custom items in MCO and renamed goods 3D.
VanillaTweaks	Vanilla Tweaks	-	Contains useful and fun modules for modern gameplay. Some modules are considered cheating!
Delta's Stacked Items	Planet Minecraft	-	Changes icons of stacked items and blocks in the inventory. Better visuals for some items with multiple variants.

User:Eevee 27/1.21.1 Porting Guide

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