How to add Cross-Origin-Embedder-Policy on Vercel

Last updated November 11, 2026 · Reviewed by a CISSP-certified security practitioner

To add Cross-Origin-Embedder-Policy on Vercel, set the header in vercel.json with the value require-corp. Requires embedded resources to opt in (enables cross-origin isolation). Commit and redeploy; headers apply on the next deployment. Then confirm it with curl -I or a free FixSecurityHeaders scan.

What does Cross-Origin-Embedder-Policy do?

COEP makes the page refuse cross-origin resources that haven't opted in via CORP or CORS. Combined with COOP it enables cross-origin isolation.

Risk if missing: Informational: mainly needed for SharedArrayBuffer and high-precision timers.

What is the Vercel configuration?

Add this to vercel.json:

vercel.json

{
  "headers": [
    {
      "source": "/(.*)",
      "headers": [
        {
          "key": "Cross-Origin-Embedder-Policy",
          "value": "require-corp"
        }
      ]
    }
  ]
}

How do I add it step by step?

Open vercel.json.
Paste the Cross-Origin-Embedder-Policy configuration shown below.
Commit and redeploy; headers apply on the next deployment.
Run curl -I https://yourdomain.com and look for the cross-origin-embedder-policy line.
Scan your site on FixSecurityHeaders to confirm the grade improved.

How do I verify it worked?

terminal

curl -sI https://yourdomain.com | grep -i "cross-origin-embedder-policy"
# expected:
# cross-origin-embedder-policy: require-corp

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What are the common mistakes?

Easily breaks third‑party images, fonts and embeds. Consider credentialless, and only deploy if you need isolation.
vercel.json headers don't apply to Next.js middleware responses — set them in next.config.js for Next apps.
The source pattern "/(.*)" matches every path.

Quick reference

Header	`Cross-Origin-Embedder-Policy`
Recommended value	`require-corp`
Stack	Vercel
Where	vercel.json
Compliance	OWASP ASVS V14.4

FAQ

What value should I use for Cross-Origin-Embedder-Policy?

A safe default is require-corp. Easily breaks third‑party images, fonts and embeds. Consider credentialless, and only deploy if you need isolation.

Why isn't Cross-Origin-Embedder-Policy showing up on Vercel?

vercel.json headers don't apply to Next.js middleware responses — set them in next.config.js for Next apps. Also clear any CDN or page cache, and check you edited the config that actually serves your domain.

Does Cross-Origin-Embedder-Policy affect SEO or performance?

No measurable performance cost — it's a few bytes per response. It doesn't affect rankings directly, but a misconfigured policy can break page resources, so test before enforcing.

Which compliance frameworks reference Cross-Origin-Embedder-Policy?

OWASP ASVS V14.4.