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Guide

How to Make Your Minecraft Bedrock Mod Work on Realms

October 20, 2025 8 min read

You've built a mod. It works perfectly in single-player. Now you want to share it with friends on your Realm. Should be easy, right? Upload it and go?

Sometimes yes. Sometimes you'll spend an hour troubleshooting why it won't activate, why custom mobs don't spawn, or why the Script API throws errors that didn't happen locally. This guide walks through the entire process — from uploading to troubleshooting — so your mod works on Realms the first time.

Step 1: Test Locally First (Seriously)

Before touching Realms, make absolutely sure your mod works in a local world. Create a new world, apply both the behavior pack and resource pack, and test every feature. Realms adds its own layer of complexity — you don't want to debug mod issues AND Realms issues at the same time.

Specifically test:

  • Custom entities spawn correctly
  • Custom items appear in the inventory and function properly
  • Recipes work at crafting tables and furnaces
  • Script API features function (if your mod uses scripts)
  • Resource pack textures and models display correctly

Step 2: Import the .mcaddon

If your mod is packaged as a .mcaddon file (which is what BlockSmith generates), the import process is straightforward:

  • On Windows 10/11: Double-click the .mcaddon file. Minecraft opens automatically and imports both the behavior pack and resource pack. You'll see "Import successful" messages.
  • On mobile (iOS/Android): Tap the .mcaddon file. It should open in Minecraft. If it doesn't, try opening Minecraft first, then tapping the file. On Android, you may need a file manager that recognizes the .mcaddon extension.
  • On console (Xbox/PlayStation/Switch): You can't directly import .mcaddon files on console. You need to apply the packs to a world on PC or mobile first, then upload that world to the Realm. Console players can then join the Realm and use the mod.

After import, the packs appear in your global pack lists: the behavior pack in "Behavior Packs" and the resource pack in "Resource Packs" when editing any world.

Step 3: Apply Packs to Your Realm

Here's where it gets Realms-specific:

  1. Open your Realm settings. From the Play screen, click the pencil/edit icon next to your Realm.
  2. Go to Behavior Packs. Find your mod's behavior pack in the "Available" list and activate it. If it doesn't appear, the import didn't register — try reimporting the .mcaddon.
  3. Go to Resource Packs. Activate the matching resource pack. Most mods require BOTH packs to function.
  4. Check for dependencies. If the behavior pack has dependencies (like the Script API modules), Realms will show them. Make sure all dependencies are satisfied.
  5. Save and restart the Realm. Pack changes require the Realm to restart. This happens automatically when you save settings, but it may take a minute.

The "Replace World" Method

If the above doesn't work (some Realms configurations are finicky about pack activation), use the nuclear option:

  1. Create a local world with the packs already activated and working
  2. In Realm settings, choose "Replace World" and select your local world
  3. This uploads the entire world including the active packs

Warning: this replaces the existing Realm world. Download a backup first.

Step 4: Enable Experiments (If Required)

Some mod features require experimental toggles. As of late 2025, most stable features don't need experiments, but some newer Script API features and custom block behaviors might.

To enable experiments on a Realm:

  • You must use the "Replace World" method — experiments can only be enabled on world creation or replacement, not after the fact
  • Create a local world with the needed experiments enabled
  • Verify the mod works locally with those experiment settings
  • Replace the Realm world with your local world

Common experiments that mods might need:

  • Beta APIs: Required for some newer Script API features that haven't graduated to stable
  • Custom Biomes: For mods that modify or add biomes (limited support)

If your mod only uses standard entity definitions, items, recipes, and stable Script API features, you probably don't need any experiments.

Step 5: Script API on Realms

Script API mods DO work on Realms, but with some important notes:

  • Scripts run server-side on the Realm. This is good — it means only the Realm owner needs the behavior pack. Players joining don't need to install anything (they'll be prompted to download the resource pack automatically).
  • Performance matters more. Realms have limited server resources. Scripts that are fine on your gaming PC might lag on Realm hardware. Keep tick-based operations efficient. Avoid scanning large block areas every tick.
  • No console output. You can't see console.log() output on Realms like you can locally. Use in-world indicators (title text, actionbar messages, particles) for debugging.
  • Dynamic properties work. World and entity dynamic properties save and persist on Realms just like locally.
  • @minecraft/server-ui works. Forms and dialogs display correctly for all connected players.

Realms Script API Gotchas

  • Watchdog is stricter. If your script takes too long in a single tick, the Realm's watchdog terminates it faster than local worlds. Optimize heavy operations by spreading them across multiple ticks using system.runTimeout().
  • Player join timing. On Realms, there can be a delay between a player "connecting" and being fully loaded. Scripts that run logic on player join should add a small delay (20-40 ticks) before interacting with the new player's entity.
  • Chunk loading differences. Realms keep chunks loaded differently than local worlds. Your mob spawning and block detection logic might behave slightly differently due to which chunks are active.

Troubleshooting Common Issues

"My mod isn't showing up in the pack list"

  • Reimport the .mcaddon file. Sometimes the first import fails silently.
  • Check that the manifest.json has valid UUIDs. Duplicate UUIDs with other installed packs will cause conflicts.
  • On mobile, check that the packs were imported to the correct Minecraft installation (not a preview/beta version).

"Custom mobs don't spawn"

  • Spawn rules are the usual culprit. Make sure your spawn rule file exists and references the correct entity identifier.
  • Check biome requirements. Your Realm might be in a biome your mob doesn't spawn in.
  • Population caps. If the monster pool is full (lots of vanilla mobs), your custom mob won't spawn until some despawn.
  • Use /kill @e[type=!player] to clear existing mobs and free up spawn slots for testing.

"Textures are missing (pink/black checkered)"

  • The resource pack isn't activated. Both behavior AND resource packs must be active.
  • Players need to accept the resource pack download prompt when joining the Realm.
  • If a player has a cached old version of the resource pack, they need to delete it from their device's resource pack storage and rejoin.

"Scripts throw errors on Realms but work locally"

  • Check the Script API version in your manifest. Realms might be running a slightly different Minecraft version than your local install.
  • Avoid using features marked as beta/@beta unless you've enabled the Beta APIs experiment.
  • Test with the exact same Minecraft version locally that the Realm is running.

"The mod works for the Realm owner but not other players"

  • Resource pack not downloading. Check that the resource pack is activated on the Realm (not just the behavior pack).
  • Script-based features should work for all players since scripts run server-side. If they don't, check for player-specific logic that might only target the host.
  • Some client-side features (custom sounds, particles) require the resource pack to be downloaded. Make sure joining players accept the download.

Testing with Friends

Before going live on your main Realm, consider these testing strategies:

  • Use a Realm backup slot. Realms support multiple world slots. Upload your modded world to an empty slot instead of replacing your main world.
  • Test with 2-3 players first. Multiplayer can expose issues that single-player doesn't: entity sync, script performance under multiple players, UI forms displayed to the wrong player.
  • Test the full flow: Join → play with mod → leave → rejoin. Some issues only appear after reconnecting (dynamic property loading, scoreboard initialization).
  • Have a non-owner test. The Realm owner has operator permissions by default. Test as a regular player to make sure permissions aren't hiding issues.

Best Practices for Realms-Compatible Mods

  • Keep scripts efficient. Target under 5ms per tick for all script operations combined.
  • Use stable APIs only. Avoid @beta features unless absolutely necessary — they require experiments which complicate Realm setup.
  • Test on mobile too. Many Realm players are on phones. If your mod works on PC but crashes mobile clients, half your friends can't play.
  • Include clear documentation. Tell players what the mod does, how to use custom items, and what to expect. A brief instructions file or in-game help command saves you from answering the same questions repeatedly.
  • Version your packs. Update the version number in manifest.json every time you change the mod. This helps Realms detect updates and prompts players to redownload resource packs.

Generate Realms-Ready Mods

Mods generated by BlockSmith are built for compatibility. The generated .mcaddon includes properly structured behavior and resource packs with valid manifests, correct dependencies, and stable API usage. Import, activate, and play — on your world or your Realm.

⚒ Build Realms-Ready Mods