Node "WebAssembly.compile ... module compile failed" in CI

Node failed to compile a WebAssembly module. The .wasm bytes were corrupted, not bundled correctly, or used a Wasm feature the runtime does not support.

What this error means

A tool backed by Wasm (an esbuild-wasm variant, a parser, a crypto lib) fails with "WebAssembly.compile(): ... module compile failed". It works locally where the asset is intact.

CompileError: WebAssembly.compile(): expected magic word 00 61 73 6d,
found 3c 21 44 4f @+0
    at async compileWasm (node:internal/...)

Common causes

The .wasm asset was not bundled as binary

A bundler treated the .wasm file as text/JS or did not emit it, so the bytes are wrong (often an HTML 404 page captured instead).

Truncated or feature-incompatible module

A partial download, or a module compiled with Wasm features the Node version lacks, fails the compile.

How to fix it

Bundle .wasm as a binary asset

Configure the bundler to emit .wasm as a file/binary loader so the bytes reach the output intact.

esbuild.build({
  loader: { '.wasm': 'file' },
  // ensure the emitted .wasm path matches the runtime fetch
});

Use a Node version that supports the features

Upgrade Node so the Wasm feature set (SIMD, threads) the module needs is available, and verify the asset is not truncated.

1. Confirm the magic bytes start with 00 61 73 6d, not an HTML page.
2. Pin a Node version supporting the required Wasm features.
3. Re-fetch the asset to rule out truncation.

How to prevent it

• Emit .wasm with a binary/file loader, never as text.
• Verify the asset path resolves (no 404 captured as the module).
• Use a Node version that supports the Wasm features in use.

Related guides