Use vw and vh units in CSS for responsive layouts. 1vw equals 1% of the viewport width, and 1vh equals 1% of the viewport height. Use vw for scaling widths and font sizes based on screen width, such as hero text or container widths. Use vh for vertical spacing and full-screen sections like landing pages by setting height: 100vh. Be cautious with vw and vh on small UI elements, accessibility-sensitive text, and scrollable containers. Combine them with clamp(), media queries, or other units like px, em, rem for better control. Avoid overusing them and apply thoughtfully for dynamic scaling effects.
You should use vw and vh units in CSS when you want elements to scale based on the size of the browser window. These units are especially useful for creating responsive layouts or visual effects that adapt to different screen sizes.
What vw and vh actually mean
-
1vwequals 1% of the viewport’s width. -
1vhequals 1% of the viewport’s height.
This means if the browser window is wider, something sized with vw will grow, and the same goes for vh and height changes. It's not tied to the content or parent elements — it's always relative to the visible area of the screen.
When to use vw for layout and typography
Using vw can be a good choice when you want an element’s width (or font size) to change as the screen gets wider or narrower.
Some common uses:
- Making headers or hero text scale with screen width
- Setting container widths that stretch with the viewport
- Creating full-width sections without using
width: 100%
Example:
If you're designing a hero banner and want the heading to feel big on large screens but not overwhelming on small ones, try setting the font-size like this:
h1 {
font-size: 5vw;
}This way, the text grows smoothly with the screen size without media queries.
?? Just keep in mind that very small or very large screens can make vw-based text too tiny or huge. You might want to combine it with clamp() or media queries for better control.
When to use vh for vertical spacing and full-screen sections
Use vh when you care about the height of the viewport — especially when building full-screen sections like landing pages or intro blocks.
For example:
- Making a section exactly the height of the screen (
height: 100vh) - Positioning elements based on screen height
- Animating elements into view based on screen size
A common case is the "full-page hero" layout:
.hero {
height: 100vh;
display: flex;
align-items: center;
justify-content: center;
}This ensures the section takes up the entire screen height, no matter the device.
But watch out — on mobile devices, some browsers (like Safari) might treat 100vh differently due to the address bar affecting the visible height. In those cases, you might need to use 100dvh or JavaScript fallbacks.
When not to use vw and `vh
There are times when these units aren’t the best fit:
- For small UI elements like buttons or icons — they can become too big or too small
- When accessibility matters — scaling fonts purely with
vwcan break user zoom settings - Inside scrollable containers — since they’re based on the viewport, not the container
In general, don’t overdo it. Use them where dynamic scaling makes sense, and pair them with other techniques like px, em, rem, or flex/grid when needed.
That’s basically it. vw and vh are powerful tools for responsiveness, especially when used sparingly and thoughtfully.
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