# Message Relay

This recipe shows how to communicate between the service worker and a page and also using service worker to relay messages between pages.

## Difficulty
Beginner

## Use case


## Features and usage

- 
- 
- 

# Message Relay

This recipe shows how to communicate between the service worker and a page and also using service worker to relay messages between pages.

## Difficulty
Beginner

## Use case
The `postMessage` API is brilliant for passing messages between windows and `iframe`s, and now we can use the service worker's `message` event to act as a messenger.

## Features and usage

- postMessage API
- Service worker registration

Add description for message relay
Add description for message relay
