GMBK SDK

A tiny script that connects your HTML5 game to GMBK: cloud saves, scores, haptics and pause handling. Inside the app it's injected automatically; include the file so your game also runs in a normal browser while you build it, where it falls back to localStorage.

Quick start

<script src="gmbk-sdk.js"></script>
<script>
  let progress = { level: 1, best: 0 };

  GMBK.load().then((saved) => {
    if (saved) progress = saved;
    startLevel(progress.level);
    GMBK.ready();
  });

  function onPoints(score) {
    GMBK.setScore(score);           // live score (Daily leaderboard)
  }

  function onLevelComplete(score) {
    progress.level += 1;
    progress.best = Math.max(progress.best, score);
    GMBK.save(progress);
    GMBK.reportScore(score);
  }

  GMBK.onPause(() => music.pause());
  GMBK.onResume(() => music.play());
</script>

API

GMBK.ready()

Call once your game is loaded and playable. GMBK hides its loading screen.

await GMBK.load()

Returns this player’s saved progress, or null. Signed-out players get whatever they saved this session.

await GMBK.save(data)

Saves any JSON value (max 256 KB). Resolves { persisted }: false when the player is signed out (GMBK asks them to sign in). Call it at checkpoints, not every frame; writes are throttled.

await GMBK.clearSave()

Deletes this player’s save for your game.

GMBK.reportScore(n)

Records a score for leaderboards and your analytics.

GMBK.setScore(n)

The current score while a run is in progress. Call it every time the score changes; it’s cheap. It drives the score display and live leaderboard when your game is picked for the Daily.

GMBK.gameOver({ score })

Marks the end of a run. In the Daily, this ends the player’s attempt, so call it exactly when the run is really over.

GMBK.haptic('light')

Device haptics: 'light' | 'medium' | 'heavy' | 'success' | 'error'.

GMBK.onPause(fn) / GMBK.onResume(fn)

Called when the player pulls out the GMBK tab or scrolls away. GMBK already freezes requestAnimationFrame, WebAudio and media while paused; use these for timers or anything else.

GMBK.onUser(fn)

Receives { signedIn, displayName } now and whenever it changes.

GMBK.inApp

true inside the GMBK app, false when testing in a normal browser.

Supported engines

GMBK runs any game that builds for the web (HTML5 + WebAssembly), which covers nearly every engine. Upload the engine's web export folder as a zip; precompressed builds (.br / .gz) are served with the right headers, and threaded builds get cross-origin isolation for SharedArrayBuffer.

Unity

Build Settings → WebGL. Brotli, Gzip or uncompressed all work. Call the SDK via a .jslib plugin.

Godot

Export → Web. Godot 4 single-threaded and threaded exports both work; .pck files are supported.

GameMaker

Target HTML5 (or GX.games/WASM). Zip the output folder.

Defold

Project → Bundle → HTML5.

Construct 3

Export → Web (HTML5). Disable offline/service-worker support.

Phaser, PixiJS, Three.js, Babylon.js

Ship your production build folder with index.html at the top.

PICO-8

export mygame.html, then zip the .html and .js.

C, C++, Rust (Emscripten / wasm-bindgen)

Compile to WebAssembly with an HTML shell page.

Bundle rules

• A .zip with index.html at the top level (a single wrapping folder is fine). Up to 15 MB unzipped and 500 files for now.
• Landscape only. Size your canvas to the window and handle resize.
• Bundle everything. Games run in a sandbox that blocks network requests to other sites, so external scripts, analytics and ads won't load.
• No popups, redirects, password fields or payment forms. Uploads containing them go to human review.
• Allowed file types: web code (html, js, css, json, wasm), images, audio, video, fonts and common engine data files.

How games get reviewed

Every upload is scanned automatically. Clean games go live immediately. Uploads that trip a rule (external scripts, obfuscated code, credential prompts) are held for a person to review, and players can report games from the Info screen; enough reports send a game back to review.