Cross-origin policy header builder

Client

Compose Cross-Origin-Opener-Policy, Cross-Origin-Embedder-Policy, and Cross-Origin-Resource-Policy lines for hardened deployments.

About Cross-origin policy headers

Build COOP, COEP, and CORP response headers for isolation and embed rules—in your browser. The interactive transform on this page runs in your browser tab—Toolcore does not need your paste for the core operation described above.

How to use this page

Paste or type in the main workspace, run the primary action from the toolbar, then copy or download the result. Use Load example when the page offers it, or URL prefill (?q= / ?qb=) so agents and tickets open the same input.

Limits and safety

Utilities here are for development and inspection—do not paste live production keys, PANs, or recovery codes into any browser tab you do not control.

Compose COOP, COEP, and CORP response headers for isolated contexts and resource embedding—see also HTTP headers reference.

?

require-corp plus same-origin COOP enables cross-origin isolated contexts (SharedArrayBuffer). Test embeds after deploy.

Nearby workflows on Toolcore

  • CSP header builder — Build a Content-Security-Policy header from directive fields—copy for nginx, Express, or CDN configs locally. before you trust a token, digest, or key material in production.
  • Subresource Integrity (SRI) — SHA-256/384/512 base64 integrity tokens for script and link tags—UTF-8 paste or local file; Web Crypto only. before you trust a token, digest, or key material in production.
  • HTTP headers — Common request and response header fields—names, direction, and short summaries—filterable client-side. before you trust a token, digest, or key material in production.
  • Referrer-Policy builder — Pick a Referrer-Policy value and copy the HTTP header—control referrer leakage locally. before you trust a token, digest, or key material in production.

Common use cases

  • Draft headers before enabling SharedArrayBuffer or cross-origin isolated pages.
  • Document CORP rules for static assets served from a separate origin.
  • Review COOP choices for pop-up OAuth flows (same-origin-allow-popups).

Common mistakes to avoid

  • require-corp without CORP on assets

    COEP require-corp breaks embeds unless every subresource sends a matching CORP (or CORS) policy.

  • Mixing COOP with broken third-party iframes

    Cross-origin isolated pages cannot load arbitrary cross-origin iframes—test embeds after deploy.

FAQ

Do I need all three headers?

Often only one or two apply. COOP protects your window; COEP/CORP govern embedded resources.

Does this run on a server?

No. Header lines are assembled in your tab.

Common search terms

Phrases people search for that match this tool. See the full long-tail keyword index.

  • cross origin opener policy builder
  • coep require corp header
  • cross origin resource policy same site
  • coop same origin header tool

More tools

Related utilities you can open in another tab—mostly client-side.