The backdrop-filter CSS property

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I had never heard of the backdrop-filter property until yesterday, but after a couple of hours messing around with it I’m positive that it’s nothing more than magic. This is because it adds filters (like changing the hue, contrast or blur) of the background of an element without changing the text or other elements inside.

Take this example where I’ve replicated the iOS notification style: see how the background of each of these boxes are blurred but the text isn’t?

That’s only a single line of CSS to create that faded background effect, just like this:

.notification {
  backdrop-filter: blur(3px);
}

Now it’s worth noting that browser support for this CSS property isn’t particularly well supported just yet (see below). But we’ve been trying to do this sort of filtering stuff for a really long time and so it’s great to see that progress is being made here. Chris wrote about the “frosted-glass” technique in 2014 and way back then you had to use a bunch of weird hacks and extra images to replicate the effect. Now we can write a lot less code to get the same effect!

We also get to pick from a lot more filters than just that frosted glass style. The following demo showcases all of the backdrop-filter values and how they change the background:

Each of these boxes are just separate divs where I’ve applied a different backdrop-filter to each. And that’s it! I sort of can’t believe how simple this is, actually.

Of course you can chain them together like so:

.element {
  backdrop-filter: blur(5px) contrast(.8);
} 

And this could make all sorts of elaborate and complex designs, especially if you start combining them together with animations.

But wait, why do we even need this property? Well, after reading up a little it seems that the go-to default example is a modal of some description. That’s what Guillermo Esteves was experimenting with back in 2015:

See the Pen PwRPZa by Guillermo Esteves (@gesteves) on CodePen.

I reckon we can do something much weirder and more beautiful if we put our minds to it.

A note about browser support

The backdrop-filter property is not well supported at the time of this writing. And even in Safari where it is supported, you’ll still need to prefix it. There’s no support for Firefox at all. But, really, do websites need to look exactly the same in every browser?

Further reading

• backdrop-filter on MDN
• Building iOS-like transparency effects in CSS with backdrop-filter

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