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Using the CSS3 vh (viewport-height) Unit

I’ve recently fallen in love with the CSS3 vh property. (vh stands for “viewport-height.”) It lets you make things a certain percentage of the height of your browser window itself—whether that “viewport” is a tablet screen, a phone screen (in portrait or landscape), a laptop, a desktop, a smart fridge(?), or what have you.

In this text and video Quick Guide, we’ll demo a use of the vh unit and show you the code behind it.

How to Use CSS3’s vh Unit: Video Demo

Here’s a video tutorial diving into vh:

What vh is Good For

Want a demo? Here’s an image that is 90% as tall as your browser—meaning you can always see the whole thing without scrolling!

How to Use the CSS vh (viewport-height) Unit: Code Demo

Here’s the complete code for the image above:

<div style="background: url(''); background-size: cover;  background-position: 50% 50%; height: 90vh;" /></div>

The most important thing to note is simply the height: 90vh; on the div itself. That’s what tells the div to be just slightly less tall than your browser is.

There are also some background-image shenanigans to make sure that the image, which is landscape-oriented, clips rather than distorting in this potentially-very-lipstick-tube-shaped post content. That’s a detail, though—the cool stuff is simply setting element sizes with vh.

Where I Think the vh Unit is Useful in Web Development

This feels like the height: 100%; CSS element that should’ve worked the whole time—although, sadly, it only works relative to the browser. (For more options that are relative to a containing element, have a look at Flexbox.)

I can see this being huge (if it isn’t already—the property’s not new, just new to me) for people developing single-page layouts with a full-page hero image and multiple full-page sections, preferably without dipping into the Big Bag of Ugly and Fragile jQuery Hacks. I can also see it being really big for very simple and device-dependent mobile app layouts, whether “app-like” but browser-based or actually native with a tool like React Native.

Thanks for reading!

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Fred Meyer

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