Browser SharedArrayBuffer Cross-Origin Isolation Error — What It Means & How to Fix It

Fix SharedArrayBuffer unavailable error in browsers requiring cross-origin isolation headers for high-resolution timer security. This guide covers everything you need to know about this topic, including common causes, step-by-step solutions, and answers to frequently asked questions.

Here are the key things to understand: SharedArrayBuffer was restricted after Spectre CPU vulnerability disclosure in 2018. Browsers now require cross-origin isolation headers to enable SharedArrayBuffer. This affects WebAssembly applications, game engines, and any code using shared memory threading. Without proper headers, typeof SharedArrayBuffer returns 'undefined' in the browser. Understanding these fundamentals will help you diagnose and resolve this issue more effectively.

The most common reasons this occurs include: Missing Cross-Origin-Embedder-Policy: require-corp header on the page. Missing Cross-Origin-Opener-Policy: same-origin header on the page. Third-party resources (images, scripts, iframes) not serving CORP headers. CDN or reverse proxy stripping the required cross-origin isolation headers. Identifying the root cause is the first step toward finding the right solution.

To resolve this, follow these recommended steps: Add both headers to your server responses: Cross-Origin-Embedder-Policy: require-corp and Cross-Origin-Opener-Policy: same-origin. Ensure all cross-origin resources include Cross-Origin-Resource-Policy: cross-origin header. For resources you do not control, use credentialless: Cross-Origin-Embedder-Policy: credentialless (Chrome 96+). Check isolation status: self.crossOriginIsolated returns true when properly configured. If these steps do not resolve the issue, consider consulting additional resources or a qualified professional.

This article is part of our Browser Errors collection on Error Codes Wiki. We provide comprehensive, up-to-date information to help you find solutions quickly.