CSS

CSS Inset Borders at Varying Depths

Sometimes when creating inset borders, we want to set them at different distances from the edge of the element. In CSS, there are a number of ways to do this, which can all be useful depending on the situation you find yourself in.

Let's look at the different ways to create inset borders with CSS.

Option 1: Using inset borders

Before Inset With Inset Border

The easiest way to make an inset border in CSS with the the border property:

button {
    border: 2px inset rgba(255,255,255,0.5);
}

Option 2: Using outlines

Before Inset With Inset Border

If that doesn't work, we can also use outlines. We can also set an offset for the outline, so that it starts within the element. This is easy to do - it only requires two lines of code:

button {
    outline: 1px solid rgba(255,255,255,0.5);
    outline-offset: -6px;
}

Option 3: Pseudo Elements

Before Inset With Inset Border

In some cases, the easiest way to do the job - pseudo elements look a bit like this:

button {
    position: relative;
}
button:before {
    content: '';
    position: absolute;
    top: 6px;
    left: 6px;
    border: 1px solid rgba(255,255,255,0.5);
    border-radius: 100px;
    width: calc(100% - 13px);
    height: calc(100% - 13px);
    z-index: 999;
}

How this works

• First, a pseudo element is a "fake" element made by CSS which is created within any HTML tag. There are two - :before, and :after - so any HTML element can have two pseudo elements.
• Above, we created one within every button element. It's position is absolute, so it sits on top of the button, instead of within it. It moves according to where the button is, as the button has its position set to relative. We then position it 6px from the top and left of the button.
• Next, we give it a border, and a border-radius so it has curved edges. We set the width and height of the element to the width or height of the element minus the distance we moved it (taking into account we are moving it "inset" by 12px as we moved it to the left by 6px), and adding the border width, so (6px + 6px + 1px)
• Finally, we set the z-index-- the vertical order of elements, so the pseudo element sits atop the button, giving us our nice outline.

Option 4: Box-shadow inset borders

Before Inset With Inset Border

Instead of using psuedo elements, in some cases we can use box-shadow:

button {
    box-shadow: inset 0 0 0 5px #e94d71, inset 0 0 0 6px rgb(255 255 255 / 50%);
}

In the above example, we put one inset box shadow which is inset 1px more, which is our border color. On top of that, we place another box shadow which is the color of the original button. This gives the illusion of an inset border.

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