Iframe Helper SDK

Secure, structured communication between a parent page and cross-domain iframes.

Embed iframes from separate origins without reaching for window.postMessage directly. The SDK handles origin validation, handshake verification, message queueing, and typed request/response contracts — so you can focus on what the iframe does instead of how to talk to it.

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Key Features

• Strict origin enforcement — exact origin matching, no wildcards. The SDK rejects '*' and verifies every message source against the configured origin.
• Bounded message queue — requests sent before the handshake completes are queued automatically and flushed once the bridge is ready. Configurable size limit prevents unbounded memory growth.
• Request/response with timeouts — every request gets a timeout, and timed-out operations are cleaned up so they can't interfere with future communication.
• Compile-time typed contracts — optional createTypedIframeBridge provides full TypeScript narrowing for method names, payloads, and responses without any runtime cost.
• Fire-and-forget events — send events to the iframe (or listen for inbound events) as one-way notifications with no response overhead.
• Optional plugins — add tree-shakable parent-side behavior such as child-driven resize through documented plugin subpaths.
• Diagnostics built in — plug in a diagnostic recorder to capture lifecycle events, message routing, and errors for debugging and monitoring.
• Zero dependencies — the runtime payload is a single ES2020 bundle with no external dependencies.
• ~2 KB gzipped — small enough to not matter in your bundle budget.

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Why Use This Library

Raw postMessage Is Error-Prone

The browser gives you window.postMessage and message events. That's a firehose. Every tab, extension, and iframe on the page uses the same channel. Without discipline you end up with:

• Messages leaking between unrelated iframes
• No handshake guarantees — you send requests to an iframe that hasn't loaded
• Origin validation bugs ('*' is easy, event.origin === expected is harder)
• Ad-hoc message formats that diverge between teams
• No timeout management, no queuing, no error taxonomy

This SDK Gives You a Protocol

Instead of raw postMessage, you get a bridge instance bound to one iframe, one origin. It manages the handshake, queues messages, enforces timeouts, and surfaces errors with structured codes you can branch on.

Concern	Raw postMessage	Iframe Helper SDK
Origin validation	Manual, easy to misconfigure	Exact origin enforced per bridge
Handshake	None, or DIY	Ready-first handshake with timeout
Message format	Ad-hoc JSON	Standardized envelope (bridge protocol)
Request queueing	Not built in	Bounded queue, automatically flushed
Timeouts	Must implement yourself	Configurable per-operation timeouts
Typed contracts	Manual type assertions	Compile-time narrowing via contracts
Error handling	Generic Error	IframeBridgeError with code-based branching
Diagnostics	console.log debugging	Pluggable diagnostic recorder and logger

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At a Glance

import { createIframeBridge } from 'iframe-helper-sdk';

const bridge = createIframeBridge({
  container: '#partner-frame',
  src: 'https://partner.example/app',
});

await bridge.whenReady();
const user = await bridge.request('user:get', { id: '123' });

Three steps: create a bridge, wait for the iframe to say it's ready, start sending requests. The bridge handles origin verification, session routing, queueing, and cleanup behind the scenes.

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Who Is This For

You're embedding an iframe that lives on a different origin (or the same origin, under controlled conditions) and you want structured communication with it. The SDK is for the parent page. The iframe application does not need to import this package — it only needs to follow the wire protocol for the handshake and message format.

Use this SDK if you:

• Embed a partner widget, chat panel, or micro-frontend from a separate domain
• Want type-safe method contracts between your app and an embedded iframe
• Need origin enforcement and message routing that's auditable and debuggable
• Maintain a platform that third parties embed into

You probably don't need this SDK if:

• Your iframe is purely presentational (no communication needed)
• You're building a single-team monolith where same-origin postMessage suffices
• You're on the iframe side only — the SDK runs in the parent context

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Next Steps

• Getting Started — Install the SDK and create your first bridge in under 5 minutes.
• Core Concepts — Understand the lifecycle, handshake, and communication patterns.
• Plugins — Add optional behavior such as child-driven iframe resize.
• GitHub — Source code, issues, and contributing.