Override body style for content in an iframe

The below only works if the iframe content is from the same parent domain.

The following jquery script works for me. Tested on Chrome and IE8. The inner iframe references a page that is on the same domain as the parent page.

In this particular case, I am hiding an element with a specific class in the inner iframe.

Basically, you just append a style element to the head section of the document loaded in a frame:

frame.addEventListener("load", ev => {
    const new_style_element = document.createElement("style");
    new_style_element.textContent = ".my-class { display: none; }"
    ev.target.contentDocument.head.appendChild(new_style_element);
});

You can also instead of style use a link element, for referencing a stylesheet resource.

An iframe is a 'hole' in your page that displays another web page inside of it. The contents of the iframe is not in any shape or form part of your parent page.

As others have stated, your options are:

• give the file that is being loaded in the iframe the necessary CSS
• if the file in the iframe is from the same domain as your parent, then you can access the DOM of the document in the iframe from the parent.

You cannot change the style of a page displayed in an iframe unless you have direct access and therefore ownership of the source html and/or css files.

This is to stop XSS (Cross Site Scripting)

This code uses vanilla JavaScript. It creates a new <style> element. It sets the text content of that element to be a string containing the new CSS. And it appends that element directly to the iframe document's head.

Keep in mind, however, that accessing elements of a document loaded from another origin is not permitted (for security reasons) -- contentDocument of the iframe element will evaluate to null when attempted from the browsing context of the page embedding the frame.

var iframe = document.getElementById('the-iframe');
var style = document.createElement('style');
style.textContent =
  'body {' +
  '  background-color: some-color;' +
  '  background-image: some-image;' +
  '}' 
;
iframe.contentDocument.head.appendChild(style);