Cross-domain iframe resize

javascript

iframe-resize

postmessage

browser-compatibility

byAnton Shumikhin·Feb 4, 2025

To resize a cross-domain iframe effectively, we use the postMessage method. The parent page adjusts the iframe height based on a received message which includes the dimensions required.

Parent page (Let's make sure we're security-savvy here):

window.addEventListener('message', (e) => {
    if (e.origin === 'http://trusted-origin.com') { // Hey, it's a friend!
        document.getElementById('myIframe').style.height = `${e.data}px`; // Stretch the legs a bit!
    }
}, false);

Iframe content (Like whispering in parent's ear):

parent.postMessage(document.body.scrollHeight, 'http://parent-origin.com');  // How tall am I now?

Don't forget to replace trusted-origin.com and parent-origin.com with your trusted domain to make a secure communication field.

Surviving the loading jungle

Different iframes load content at varying speeds. To create the perfect resize, we need to kickstart the postMessage post the iframe content load completion. We can rely on our dependable window.onload event. Set a minimum height at the start to avoid any unexpected display glitches when the content is being loaded.

Here's an example with a bit of humor:

window.onload = () => {
    parent.postMessage(document.body.scrollHeight, 'http://parent-origin.com'); // I'm fully grown now, Parent!
};

Keep your friends close, and your origins closer

While the wildcard "*" in postMessage's target origin seems tempting as it allows you to send messages to any parent iframe, beware! It's like an open gate for invaders. It's safer to validate your target origin or maintain a list of allowed domains.

The Sherlock Holmes' debugging chronicles

Everyone enjoys some insights while debugging. The console.log(string) function is our tiny detective for the day. Log your incoming and outgoing messages to track the flow and spot any unexpected behavior.

Libraries to our rescue

If you're into a hands-off approach, the iframe-resizer library can be your friend. This library supports multiple iframes and handles dynamic content. Plus, the autoResize feature takes care of automatic adjustments for you. A real gentleman, isn't it?

Consistency is key

Consistency in behavior across all browsers and HTTPS for a secure communication line are must-haves for your solution. A simple HTML structure can boost performance, reducing load time or rendering issues. However, remember to test for browser compatibility, especially with event handling methods.

explain-codes / Javascript / Cross-domain iframe resize

Linked

How do you use window.postMessage across domains?

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How to communicate between iframe and the parent site?

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Adjust width and height of iframe to fit with content in it

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Make iframe automatically adjust height according to the contents without using scrollbar?

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Resizing an iframe based on content

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