Install J2B MC #
Install Fabric Loader for 1.21 (plus Fabric API if the downloads page asks for it), place the JAR in your mods folder, and launch with the Fabric profile.
- Install the J2B MC mod for your 1.21.x version (1.21 → 1.21.11 published on v3.2.1; 26.x builds are blocked upstream — no mappings).
- Bedrock-ify a world: press the Bedrock-ify button at world creation, or toggle it later on an existing world from the config screen.
- Open the config screen (B key or Mod Menu) and pick your flags — 27 flags govern the 161 sub-systems across 13 phases.
- Explore the /j2b command suite for in-game control.
- Try PvP and redstone changes first in a test world — combat (attack cooldown, knockback, crits), movement, physics, mob AI and redstone all move toward Bedrock behaviour.
- Import a Bedrock .mcworld file into a Java world when you want Bedrock terrain in Java.
- For cross-edition connectivity, run /j2b connect <host> <port> — online Bedrock auth is still being verified against real servers.
Working with J2B MC #
Product-specific steps, separate from the general install guide above.
Bedrock-ify a world
Use the **Bedrock-ify button at world creation**, or toggle it later on an existing world from the config screen (**B** key or the Mod Menu entry) so Bedrock mechanics apply in Java. One press toggles Bedrock-style gameplay across **161 sub-systems** in **13 phases** — combat, physics, movement, mob AI, redstone, enchanting, food and more.
What you'll see. At world creation a Bedrock-ify button sits beside the world options. On an existing world, the config screen (B key) lists the 27 toggleable flags that govern the 13 phases.
Pick your flags
Each mechanic group is governed by one of **27 flags** — open the config screen (**B** key or Mod Menu) to pick what you want. PvP changes are real: attack cooldown, knockback and crits move toward Bedrock behaviour, alongside movement, physics, mob AI and redstone changes.
- Everything is individually toggleable — 161 sub-systems, 27 flags.
- Explore and control the mod from the /j2b command suite.
- The core is validated against all 12 versions with a zero-crash-risk feature-parity matrix.
Join Bedrock servers
Connect Java → Bedrock directly with the native **RakNet** client (ECDH + AES-256-CFB8 encryption):
/j2b connect <host> <port>Tips
- Import Bedrock .mcworld files into Java worlds when you want Bedrock terrain in Java.
- Validate each flag in a test world before enabling a whole phase on a survival world.
Common problems
Real-server joins are not verified yet
26.x build is missing
Folder locations by platform #
| Platform | mods / resourcepacks folder | config folder |
|---|---|---|
| Windows | %appdata%\.minecraft\mods · \resourcepacks | %appdata%\.minecraft\config |
| macOS | ~/Library/Application Support/minecraft/mods | ~/Library/Application Support/minecraft/config |
| Linux | ~/.minecraft/mods · ~/.minecraft/resourcepacks | ~/.minecraft/config |
MultiMC / Prism users: these folders live inside Instances/<instance>/.minecraft/. Match the build to your exact Minecraft version — the compatibility table in the docs lists every supported version.
Configure #
Settings live in the config folder (JSON5 files you can edit by hand) and, where available, in the in-game settings screen the mod adds. The exact keys and keybinds are listed in the documentation and the FAQ below.
Tips for J2B MC #
- Keep J2B MC on the version range shown on its product page.
- If it doesn't load, confirm the JAR is in the right mods folder for the launcher and version you chose.
- Bedrock Edition, mobile, and console can't run Java Edition mods or packs — for a port or custom variant, request a commission.