How Can I Create Angled Corners in CSS Using Only :before and :after Pseudo-elements?

Angled Corners in CSS: A Detailed Solution

Creating angled corners using pure CSS is possible, although it presents certain challenges. To achieve this, it's necessary to utilize :before and :after elements within a parent container that has a border.

1. Add a Border to the Container: Establish a border around the container element to define the visible boundary.
2. Create a :before Element to Block a Corner: Add a :before element with a border-top style specified in pixels to create a solid perpendicular line. Offset this element by -1 pixel to account for the border of the container.
3. Add a :after Element to Create an Inner Line: Introduce a :after element with a slightly smaller offset than the :before element. Set the border-top style of the :after element to a different color, such as white, to create a contrasting line within the cut-off area.

While this technique approximates the desired effect, it may introduce a slight issue with the thickness of the 45-degree line.

Example Code:

.cutCorner {
    position:relative; background-color:blue; 
    border:1px solid silver; display: inline-block;
}

.cutCorner img {
    display:block;
}

.cutCorner:before {
    position:absolute; left:-1px; top:-1px; content:'';
    border-top: 70px solid silver;
    border-right: 70px solid transparent;
}

.cutCorner:after {
    position:absolute; left:-2px; top:-2px; content:'';
    border-top: 70px solid white;
    border-right: 70px solid transparent;
}

<div class="cutCorner">
    <img  src="/static/imghwm/default1.png" data-src="https://www.google.co.uk/logos/doodles/2013/william-john-swainsons-224th-birthday-5655612935372800-hp.jpg" class="lazy" alt="How Can I Create Angled Corners in CSS Using Only :before and :after Pseudo-elements?" >
</div>

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