Enabling Experiments by Editing World NBT

Normally, enabling an experimental toggle in the Minecraft Bedrock menu forces the game to create a copy of your world if that world has already been opened. When you are iterating quickly on a behavior pack or updating an existing world template, constantly managing copied world folders becomes tedious and error-prone.

Direct NBT editing is also essential for Bedrock Dedicated Server (BDS) administrators. The `server.properties` file does not expose individual add-on experiment toggles like Beta APIs or Upcoming Creator Features. To run an experimental pack on a server, you must either create the world locally, flip the switches, and upload it, or edit the server's `level.dat` file directly using an external tool.

Every Bedrock world folder contains a file named `level.dat` at its root. Unlike Java Edition, which uses a big-endian GZip-compressed NBT format, Minecraft Bedrock's `level.dat` is uncompressed, stored in little-endian byte order, and begins with an 8-byte header (4 bytes for the storage version and 4 bytes for the payload length). Because of this header, standard Java NBT editors will fail to open the file unless they specifically support Bedrock formats.

Before touching `level.dat`, close the world completely—or stop the dedicated server process—and make a backup copy of the file. Open `level.dat` in a Bedrock-capable NBT editor. At the root of the NBT tree, look for a Compound tag named `experiments`. If the world has never had an experiment enabled, this compound tag might be empty, or you may need to create it yourself under the root compound.

Inside the `experiments` compound tag, each experimental toggle is stored as a `TAG_Byte` (which acts as a boolean: `1` for true, `0` for false). In addition to the individual feature flags, there are two metadata bytes that control how the game treats the world as a whole: `experiments_ever_used` and `saved_with_toggled_experiments`.

When enabling an experiment manually, you must add or set the specific feature's byte tag to `1`, and you must also set both `experiments_ever_used` and `saved_with_toggled_experiments` to `1`. If you forget the two metadata flags, Minecraft may ignore the individual feature toggles when loading the world, or fail to mark the world as experimental.

The most common reason to edit `level.dat` is to enable the `gametest` byte so your world can run scripts that depend on Beta APIs. Notice how the internal NBT name (`gametest`) reflects the original name of the GameTest Framework, even though the user interface now calls this toggle "Beta APIs".

Once `gametest`, `experiments_ever_used`, and `saved_with_toggled_experiments` are all set to `1` in `level.dat`, the world will accept a behavior pack `manifest.json` that declares a `-beta` version dependency without throwing a missing dependency error.

{
  "format_version": 2,
  "header": {
    "name": "Beta Script Test Pack",
    "description": "Requires the gametest NBT byte set to 1 in level.dat",
    "uuid": "6b18763e-0c42-4847-9b63-882497a19a21",
    "version": [1, 0, 0],
    "min_engine_version": [1, 21, 0]
  },
  "modules": [
    {
      "type": "script",
      "language": "javascript",
      "uuid": "c8d92b10-5b2e-4f89-993a-2b1e7c441234",
      "entry": "scripts/main.js",
      "version": [1, 0, 0]
    }
  ],
  "dependencies": [
    {
      "module_name": "@minecraft/server",
      "version": "1.14.0-beta"
    }
  ]
}

When an experimental feature graduates to stable in a new Minecraft update (or when you rewrite your script to use a stable release version of `@minecraft/server` instead of `-beta`), you may want to remove the `[Experimental]` tag from your world so players do not see warnings and achievements can function in template copies.

To strip experimental status from a world, open `level.dat`, expand the `experiments` compound, and either set every `TAG_Byte` inside it to `0` or delete all the byte tags inside `experiments`—including `experiments_ever_used` and `saved_with_toggled_experiments`. Be cautious if your world contains custom blocks or entities generated under an experiment that has not cleanly migrated to stable, as loading the world without the toggle may cause those blocks to turn into `minecraft:info_update` placeholder blocks.

Applies to all modern Minecraft Bedrock versions (1.16.100 through 1.21+). The exact byte keys inside the experiments compound change over time as Mojang introduces new preview features and retires old toggles like Holiday Creator Features.

Read out of the game itself, so the ids match the version you are building for.