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Security headers › Cross-Origin-Opener-Policy

How to add the Cross-Origin-Opener-Policy header in Vercel

COOP isolates your page's browsing context from cross-origin windows it opens or that open it.

Vercel configuration (vercel.json)

{
  "headers": [
    {
      "source": "/(.*)",
      "headers": [
        {
          "key": "Cross-Origin-Opener-Policy",
          "value": "same-origin"
        }
      ]
    }
  ]
}

Add to vercel.json at the project root and redeploy. Next.js projects on Vercel can set headers in next.config instead.

Before you deploy

same-origin can break OAuth or payment pop-ups that rely on window.opener. Use same-origin-allow-popups in that case.

Verify it works

curl -sI https://your-site.com | grep -i cross-origin-opener-policy

Or run a free Korrali Web scan to check this and every other security header at once.

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Other headers in Vercel