WebAssembly Streaming Compilation

taglib-wasm automatically leverages WebAssembly streaming APIs for optimal performance when loading from network sources.

How It Works

When you initialize taglib-wasm with a URL:

const taglib = await TagLib.initialize({
  wasmUrl: "https://cdn.jsdelivr.net/npm/taglib-wasm@latest/dist/taglib.wasm",
});

The library automatically uses WebAssembly.instantiateStreaming() when available, which provides:

1. Parallel Download & Compilation: The WebAssembly module is compiled while it's being downloaded
2. Lower Memory Usage: No need to buffer the entire WASM file before compilation
3. Faster Startup: Compilation begins as soon as the first bytes arrive

Browser Support

Streaming compilation is supported in:

• Chrome 61+
• Firefox 58+
• Safari 15+
• Edge 79+
• Deno (when loading from URLs)

Fallback Behavior

If streaming is not available or fails, taglib-wasm automatically falls back to standard ArrayBuffer instantiation:

wasm streaming compile failed: TypeError: Failed to fetch
falling back to ArrayBuffer instantiation

This ensures compatibility across all environments.

Best Practices

1. Use CDN URLs for Web Apps

// Recommended: Load from CDN with streaming
const taglib = await TagLib.initialize({
  wasmUrl: "https://cdn.jsdelivr.net/npm/taglib-wasm@latest/dist/taglib.wasm",
});

// Also good: Use your own CDN
const taglib = await TagLib.initialize({
  wasmUrl: "https://your-cdn.com/assets/taglib.wasm",
});

2. Ensure Proper Server Headers

For optimal streaming, ensure your server returns:

Content-Type: application/wasm
Access-Control-Allow-Origin: * (or specific origin)
Cache-Control: public, max-age=31536000

3. Monitor Loading Performance

console.time("TagLib initialization");
const taglib = await TagLib.initialize({
  wasmUrl: "https://cdn.jsdelivr.net/npm/taglib-wasm@latest/dist/taglib.wasm",
});
console.timeEnd("TagLib initialization");
// Typical: 200-400ms with streaming, 400-800ms without

When Streaming Isn't Used

Streaming compilation is NOT used when:

1. Loading from ArrayBuffer: When you provide wasmBinary directly
2. File System Access: When loading from disk in Node.js
3. Embedded WASM: In Deno compiled binaries
4. Unsupported Environments: Older browsers or restricted environments

In these cases, the standard instantiation path is used, which is still performant but requires the full WASM binary in memory before compilation begins.

Performance Comparison

Loading Method	Typical Time	Memory Peak	Streaming Used
CDN URL	200-400ms	~5MB	✅ Yes
Local File	100-200ms	~10MB	❌ No
Embedded Binary	150-250ms	~10MB	❌ No
ArrayBuffer	300-500ms	~10MB	❌ No

Times measured on modern hardware with fast internet connection

Technical Details

The Emscripten-generated runtime in taglib-wasm includes this streaming logic:

if (!binary && typeof WebAssembly.instantiateStreaming == "function") {
  try {
    var response = fetch(binaryFile, { credentials: "same-origin" });
    var instantiationResult = await WebAssembly.instantiateStreaming(
      response,
      imports,
    );
    return instantiationResult;
  } catch (reason) {
    // Falls back to ArrayBuffer instantiation
  }
}

This means you get streaming benefits automatically without any configuration needed!