Transferable objects

Summary

postMessage can transfer ArrayBuffer ownership zero-copy — sender neutered after transfer. Structured clone duplicates for non-transferables. Workers + transfer for large binary without copy cost. Detached buffer access throws — coordinate lifecycle.

Code example

const buffer = new ArrayBuffer(1024 * 1024);
worker.postMessage({ buffer }, [buffer]);
// buffer.byteLength === 0 in sender after transfer

Key points

• postMessage can transfer ArrayBuffer ownership zero-copy — sender neutered after transfer.
• Structured clone duplicates for non-transferables.
• Workers + transfer for large binary without copy cost.
• Detached buffer access throws — coordinate lifecycle.

Further reading

• Transferable objects
• postMessage

Related concepts

• SharedArrayBuffer
• CORS preflight internals