> For the complete documentation index, see [llms.txt](https://johnkazer.gitbook.io/core-web-dev-concepts/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://johnkazer.gitbook.io/core-web-dev-concepts/messaging.md).

# Messaging

Communication between iframes or service workers and a webpage, such as [postMessage](https://developer.mozilla.org/en-US/docs/Web/API/Window/postMessage).