Loading Assets

Loading Assets

The Phaser Loader (this.load) handles fetching all external content: images, audio, JSON, tilemaps, atlases, fonts, scripts, and more. Assets are queued in preload(), loaded in parallel, and placed into global caches accessible by every Scene.

Key source paths: src/loader/LoaderPlugin.js, src/loader/File.js, src/loader/filetypes/, src/loader/events/ Related skills: ../game-setup-and-config/SKILL.md, ../scenes/SKILL.md, ../sprites-and-images/SKILL.md

Quick Start

class GameScene extends Phaser.Scene {
    preload() {
        this.load.image('logo', 'assets/logo.png');
    }

    create() {
        this.add.image(400, 300, 'logo');
    }
}

Assets loaded in preload() are guaranteed to be ready when create() runs. The Loader starts automatically during the preload phase.

Core Concepts

The Preload Pattern

Every Scene can define a preload() method. The Loader automatically starts when preload() completes and waits for all queued files to finish before calling create().

preload() {
    // Queue files - they don't load immediately
    this.load.image('sky', 'assets/sky.png');
    this.load.spritesheet('dude', 'assets/dude.png', { frameWidth: 32, frameHeight: 48 });
    this.load.audio('jump', 'assets/jump.mp3');
}

create() {
    // All assets above are now available
    this.add.image(400, 300, 'sky');
    this.add.sprite(100, 450, 'dude');
    this.sound.play('jump');
}

Loading Outside of Preload

If you call this.load methods outside of preload() (for example, in create() or in response to a user action), you must manually start the Loader:

create() {
    this.load.image('extra', 'assets/extra.png');
    this.load.once('complete', () => {
        this.add.image(400, 300, 'extra');
    });
    this.load.start();
}

URL Resolution: baseURL, path, and prefix

The final URL for a file is resolved as: baseURL + path + filename. These can be set via the game config or at runtime.

preload() {
    // Set base URL (prepended to all relative paths)
    this.load.setBaseURL('https://cdn.example.com/');

    // Set path (prepended after baseURL, before filename)
    this.load.setPath('assets/images/');

    // Set key prefix (prepended to the cache key, not the URL)
    this.load.setPrefix('LEVEL1.');

    // Loads from: https://cdn.example.com/assets/images/hero.png
    // Cached with key: LEVEL1.hero
    this.load.image('hero', 'hero.png');

    // Absolute URLs bypass the path/baseURL
    this.load.image('cloud', 'https://other-server.com/cloud.png');
}

These can also be set in the game config:

const config = {
    loader: {
        baseURL: 'https://cdn.example.com/',
        path: 'assets/',
        prefix: '',
        maxParallelDownloads: 32,
        crossOrigin: 'anonymous',
        responseType: '',
        async: true,
        timeout: 0,
        maxRetries: 2,
        imageLoadType: 'XHR' // or 'HTMLImageElement'
    }
};

Global Caches

Assets are stored in global game-level caches, not per-Scene. An image loaded in one Scene is available in every other Scene. Textures go into game.textures (the Texture Manager). Other data goes into game.cache sub-caches (e.g., game.cache.json, game.cache.audio, game.cache.xml).

Load Events

The Loader emits events throughout the loading lifecycle. Use these for progress bars and loading screens.

preload() {
    this.load.on('progress', (value) => {
        // value is 0 to 1
        console.log(`Loading: ${Math.round(value * 100)}%`);
    });

    this.load.on('complete', () => {
        console.log('All assets loaded');
    });

    this.load.on('loaderror', (file) => {
        console.warn('Failed to load:', file.key);
    });

    this.load.image('bg', 'assets/bg.png');
}

Common Patterns

Loading Images and Sprite Sheets

preload() {
    // Single image
    this.load.image('star', 'assets/star.png');

    // Image with normal map (pass URL array: [texture, normalMap])
    this.load.image('brick', ['assets/brick.png', 'assets/brick_n.png']);

    // Sprite sheet (fixed frame sizes)
    this.load.spritesheet('explosion', 'assets/explosion.png', {
        frameWidth: 64,
        frameHeight: 64,
        startFrame: 0,
        endFrame: 23,
        margin: 0,
        spacing: 0
    });

    // SVG (optionally rasterize at a specific size)
    this.load.svg('logo', 'assets/logo.svg', { width: 400, height: 400 });
}

Loading Audio

preload() {
    // Single file
    this.load.audio('bgm', 'assets/music.mp3');

    // Multiple formats for cross-browser support
    this.load.audio('bgm', ['assets/music.ogg', 'assets/music.mp3']);

    // Audio sprite (JSON defines named regions within a single audio file)
    this.load.audioSprite('sfx', 'assets/sfx.json', [
        'assets/sfx.ogg',
        'assets/sfx.mp3'
    ]);
}

Loading JSON and Tilemaps

preload() {
    // JSON data (stored in this.cache.json)
    this.load.json('levelData', 'assets/level1.json');

    // JSON with a dataKey to extract a sub-object
    this.load.json('enemies', 'assets/data.json', 'enemies');

    // Tiled tilemap (JSON format exported from Tiled)
    this.load.tilemapTiledJSON('map', 'assets/map.json');

    // CSV tilemap
    this.load.tilemapCSV('csvmap', 'assets/level.csv');

    // Impact tilemap
    this.load.tilemapImpact('impactmap', 'assets/level.js');
}

create() {
    const data = this.cache.json.get('levelData');
    const map = this.make.tilemap({ key: 'map' });
}

Loading Atlases

preload() {
    // JSON atlas (e.g., TexturePacker JSON Hash/Array)
    this.load.atlas('sprites', 'assets/sprites.png', 'assets/sprites.json');

    // XML atlas (e.g., Starling/Sparrow format)
    this.load.atlasXML('ui', 'assets/ui.png', 'assets/ui.xml');

    // Multi-atlas (atlas split across multiple textures)
    this.load.multiatlas('world', 'assets/world.json', 'assets/');

    // Unity texture atlas format
    this.load.unityAtlas('chars', 'assets/chars.png', 'assets/chars.txt');

    // Aseprite atlas
    this.load.aseprite('knight', 'assets/knight.png', 'assets/knight.json');
}

create() {
    this.add.sprite(400, 300, 'sprites', 'walk_01');
}

Loading Bitmap Fonts

preload() {
    // Requires both a texture and XML/JSON font data file
    this.load.bitmapFont('pixels', 'assets/font.png', 'assets/font.xml');
}

create() {
    this.add.bitmapText(100, 100, 'pixels', 'Hello World', 32);
}

Loading Video

preload() {
    // Load a video file. Third arg: noAudio flag (default false)
    this.load.video('intro', 'assets/intro.mp4');

    // Load without audio track
    this.load.video('bg_loop', 'assets/loop.mp4', true);
}

Loading Web Fonts

preload() {
    // Load a font file (ttf, otf, woff, woff2)
    this.load.font('myFont', 'assets/myfont.ttf', 'truetype');

    // With optional font face descriptors
    this.load.font('boldFont', 'assets/bold.woff2', 'woff2', {
        weight: 'bold',
        style: 'normal'
    });
}

Loading a Pack File

A pack file is a JSON file that describes multiple assets to load at once. Useful for organizing asset manifests.

preload() {
    this.load.pack('pack1', 'assets/pack.json');
}

Pack file format:

{
    "section1": {
        "baseURL": "assets/",
        "files": [
            { "type": "image", "key": "bg", "url": "bg.png" },
            { "type": "atlas", "key": "chars", "textureURL": "chars.png", "atlasURL": "chars.json" }
        ]
    }
}

Loading with a Progress Bar

preload() {
    const progressBar = this.add.graphics();
    const progressBox = this.add.graphics();
    progressBox.fillStyle(0x222222, 0.8);
    progressBox.fillRect(240, 270, 320, 50);

    this.load.on('progress', (value) => {
        progressBar.clear();
        progressBar.fillStyle(0xffffff, 1);