How can I inspect and tweak :before and :after pseudo-elements in-browser?

I have created some fairly elaborate DOM elements with an :after pseudo-element, and I'd like to be able to inspect and tweak them in either Chrome Inspector or Firebug or equivalent.

Despite this feature being mentioned in this WebKit/Safari blog post (dated 2010), I can't find this feature at all in either Chrome or Safari. Chrome does at least have checkboxes to inspect :hover, :visited and :active states, but :before and :after are nowhere to be seen.

Additionally, this blog post (dated 2009!) mentions this capability exists in the IE dev tools, but I'm currently using Mac OS, so this is no help to me. Additionally, IE is not a browser I'm primarily targeting.

Is there any way of inspecting these pseudo-elements?

EDIT: In addition to being wrong about Firebug being unable to inspect these elements, I've found Opera to be pretty good at Inspecting :before and :after elements out of the box.

In Chrome's Dev tools, the styles of a pseudo-element are visible in the panel:

Otherwise, you can also input the following line in the JavaScript console, and inspect the returned CSSStyleDeclaration object:

getComputedStyle(document.querySelector('html > body'), ':before');

• window.getComputedStyle
• document.querySelector

As of Chrome 31 pseudo elements show in the elements panel as child elements of their parent as shown in the following image:

You can select them as you would a normal element but if you remove the content style then the pseudo element will also be removed and the devtools focus will change to it's parent.

It appears that inherited CSS styles are not viewable and you can't edit CSS content from the elements panel.

Chrome won't show :before and :after pseudo elements in the DOM-tree, if they miss "content" attribute. It should be set, even if it is set to nothing.

This won't show up:

:after {
  background-color: red;
}

This will show up in the inspector:

:after {
  content: "";   
  background-color: red;    
}

Hope it helps.

After a lot of frustration, I figured out that firefox doesn't show the pseudo elements in the document tree at all, but if you select the exact element which has pseudo element(s) defined, then the styles for its pseudo element(s) are shown in the style rules section on the right side. This is true for both firebug and the built-in inspect ("Q"), and I am shocked that nobody bothered to explain this clearly before.

Clearly, chrome/chromium's handling of pseudo elements is vastly superior, as they can be selected (both in the document tree and directly on the page) and inspected just like regular elements, with layout, properties and everything else, independent of their "owner".

Browser versions I'm using currently: Chromium 40.0.2214.91, Firefox 31.3.0.

At least since Chrome 62 there's a setting in DevTools to 'Show user agent shadow DOM' which displays additional pseudo-elements like input placeholders, which wouldn't show up in the DOM tree otherwise.

More information: https://stackoverflow.com/a/26853319/3963594