Engine apps: Godot and Unity games

An engine app is a game made in Godot 4.3+ or Unity 2021.3+, exported for the web and run on a token page. You upload the export folder as it is. The platform's boot component starts it, so you write no viewer code.

What runs

Single-threaded exports only. A threaded build needs cross-origin isolation, which a token page doesn't have, and Safari can't run one in an app's frame at all. So a manifest with threads: true is refused.

• Godot: export for Web with Thread Support off (Godot 4.3 or later). The export's index.html must not set GODOT_THREADS_ENABLED = true.
• Unity: the default WebGL build, which is single-threaded (Unity 2021.3 or later). Uncompressed, Brotli and Gzip builds all work.

The engine block

Add an engine block to your manifest:

{
  "engine": {
    "kind": "godot",
    "entry": "index",
    "files": ["index.js", "index.wasm", "index.pck"],
    "threads": false
  }
}

Field	What it is
kind	"godot" or "unity"
entry	The export's name without an extension, relative to engine/: Godot index, Unity Build/<name>
files	The export's files, relative to engine/ (1 to 512). Each one must be in the package's engine/ folder
threads	Must be false

A Unity example:

{
  "engine": {
    "kind": "unity",
    "entry": "Build/WebGL",
    "files": ["Build/WebGL.loader.js", "Build/WebGL.framework.js.br", "Build/WebGL.data.br", "Build/WebGL.wasm.br"],
    "threads": false
  }
}

File names may use letters, digits, spaces, ., _, - and / for folders. Folders are kept as they are, so a Unity StreamingAssets/ folder works.

The engine/ folder

Your export folder goes in engine/, beside your manifest. The package needs no bundle.js: the platform's boot component runs the export. Every file in engine/ is covered by the package's HASHES.json, like the rest of your app, and is served from your app's own version:

https://apps.chaindaddy.io/{appId}/{version}/engine/<file>

Files are stored compressed with brotli when you submit, and served with the headers the engines need (application/wasm for .wasm, so it compiles while it downloads). A Unity .br or .gz file is kept as it is and served with its own encoding. Each version's files never change, so a returning player downloads nothing.

Test locally

Run chaindaddy app dev with your export in engine/. It prints a report (threads off, the files your entry needs, and the size against the tiers). No viewer code is needed.

Once you've submitted a build, you can also play it on your own token page before it's reviewed: see Preview a build on your own token page. The preview runs the export you uploaded, for you alone, with an unreviewed build's limits.

Size tiers

Sizes are what a player downloads (brotli), for the whole engine/ folder:

Tier	Download	Who gets it
S	up to 16 MB	Every reviewed engine app
M	up to 64 MB	On request

Whatever the tier, the export may be at most 256 MB uncompressed, and 64 MB for any one file. A phone has to hold the game in memory.

Godot's engine alone is about 8 MB to download, so a small Godot game fits in S. A small Unity release build is about 6 MB.

What the frame allows

Your game runs in its own isolated frame, like every third-party app. In that frame:

• It can load its own version's files and nothing else, unless you declare net:connect with your server's origins (see App Manifest).
• Saves go through the platform. Browser storage (IndexedDB) isn't available in the frame, so a save written there is gone on reload. Keep progress with the save and load actions instead: one save of up to 256 KB per player, kept for that player on your token page. A player has to be signed in to save; a visitor who isn't loads nothing and starts fresh.
• Fullscreen comes from the platform's own button, not the engine's. Hide your engine's fullscreen button.
• Pointer lock (for mouse-look games): declare the ui:pointer-lock permission, and the engine's own pointer lock works (Godot Input.mouse_mode = Input.MOUSE_MODE_CAPTURED, Unity Cursor.lockState = CursorLockMode.Locked). The browser locks the pointer only after the player clicks the game, and Esc releases it. Without the permission, the lock is refused.
• Audio starts after the player's first tap on Safari, as on any web page.

Engine apps haven't been tested on phones yet, so don't promise players a mobile version.

Review

Submitting reads every file in engine/, not just your bundle, and refuses a threaded build (its .wasm has shared memory, or its index.html sets GODOT_THREADS_ENABLED = true) or one made before Godot 4.3 or Unity 2021.3, the version read from your .pck, or your .data and .wasm. Anything it can't read, such as a .unityweb file, a reviewer checks by hand.