iframe proxy

Proxy iframes securely with full event handling and introspection for debugging.

Overview

iframe-proxy embeds any target URL inside a transparent iframe and relays postMessage events bidirectionally between the parent window and the embedded frame. It acts as a pass-through bridge — all messages flow through without modification, while the debug panel gives you full visibility into what's being sent.

Query Parameters

url

The URL to embed. Must be a valid http: or https: URL. If omitted in non-debug mode, the page shows an error. If omitted in debug mode, an inline input appears in the top bar where you can type a URL and press Enter to load it.

/iframe-proxy?url=https://example.com

debug

Set to true to enable debug mode. When active, the iframe is inset from the edges of the viewport and a side panel opens showing every relayed message in real time.

/iframe-proxy?url=https://example.com&debug=true

In debug mode without a url param, the page can be used as a standalone tool — just type a URL into the top bar to get started:

/iframe-proxy?debug=true

Message Relay

All postMessage traffic is intercepted and forwarded:

  • parent → frame — messages from the parent window are forwarded into the embedded iframe
  • frame → parent — messages from the iframe are forwarded up to the parent window

Messages are forwarded with * as the target origin. This is intentional for a debugging proxy — do not use in contexts where origin validation is required.

Debug Panel

When debug=true, a 320px side panel appears on the right showing each relayed message with:

  • Direction indicator (parent→frame or frame→parent)
  • Timestamp
  • Full message data as formatted JSON

Example

Embed a page and watch its messages:

/iframe-proxy?url=https://my-app.example.com&debug=true

From a parent page, send a message to the embedded frame:

const proxy = document.querySelector("iframe");
proxy.contentWindow.postMessage({ type: "ping" }, "*");

The proxy relays it to the embedded frame, and the debug panel logs the exchange.