Iframe Sandbox & Cross-Origin Isolation Builder
Embedding third-party widgets, ads, or untrusted content? The sandbox
attribute and COOP/COEP headers are your primary defenses — but a single wrong flag can
either break the embed or leave you exposed. Build secure configurations visually and
get instant warnings about dangerous combinations.
Tool interface
🧩 Iframe Sandbox Builder
Sandbox Permissions
Unchecked capabilities are blocked. An empty sandbox="" is the most restrictive.
Generated Iframe Tag
🔒 Cross-Origin Isolation (COOP / COEP)
These HTTP response headers isolate your page's browsing context. They are
required to use SharedArrayBuffer and protect against
cross-origin resource leaks.
Generated HTTP Headers
Introduction
Iframes are the primary vector for embedding untrusted third-party content, and the
sandbox attribute is your main tool for containing it. Meanwhile,
cross-origin isolation via COOP and COEP has become essential for high-performance
APIs like SharedArrayBuffer. Getting either wrong has real security and
functionality consequences.
How It Works
- Each sandbox flag is presented with a risk rating and description.
- As you toggle flags, the iframe tag regenerates and a rule engine checks for dangerous combinations.
- COOP and COEP selectors generate the exact HTTP headers, with explanations for each value.
- The SharedArrayBuffer toggle auto-recommends the strict isolation configuration.
Privacy
This tool performs pure client-side string generation. No network requests are made. Your configuration is never transmitted.
Limitations
- Cannot verify that a specific third-party widget will function under the chosen restrictions — that requires live testing.
- COOP/COEP behavior can vary slightly by browser; test in your target environments.
FAQ
Why is allow-scripts + allow-same-origin dangerous?
With both flags, the iframe retains its origin and can run script. Since the sandbox attribute lives in the parent's DOM, a same-origin iframe that is also the parent's origin could remove it. For cross-origin untrusted content it's less severe, but for same-origin embeds it fully negates sandboxing.
What enables SharedArrayBuffer?
You need Cross-Origin-Opener-Policy: same-origin and Cross-Origin-Embedder-Policy: require-corp (or credentialless). This sets window.crossOriginIsolated to true.
Is my configuration uploaded?
No. Everything is generated locally in your browser. Nothing is transmitted.