Summary
Requires cross-origin isolated context (Cross-Origin-Opener-Policy, Cross-Origin-Embedder-Policy) — Spectre mitigation. Enables true shared memory with Atomics — WASM, multi-thread. Without headers, SAB is disabled in modern browsers. Breaks third-party embeds without CORP headers.
Code example
// Requires COOP + COEP headers for crossOriginIsolated
if (crossOriginIsolated && typeof SharedArrayBuffer !== 'undefined') {
const sab = new SharedArrayBuffer(1024);
worker.postMessage({ sab });
}
Key points
- Requires cross-origin isolated context (
Cross-Origin-Opener-Policy,Cross-Origin-Embedder-Policy) — Spectre mitigation. - Enables true shared memory with Atomics — WASM, multi-thread.
- Without headers, SAB is disabled in modern browsers.
- Breaks third-party embeds without CORP headers.