In web development, responsive design is one of the most critical aspects and with vw and vh you can create a visually appealing and user-friendly experience. With the growing variety of devices—smartphones, tablets, desktops, and even smartwatches—designers must ensure that their websites adapt gracefully to different screen sizes and resolutions.

For this reason, modern web developers often favour using “vw” (viewport width) and “vh” (viewport height) over the more traditional “px” (pixels) for sizing elements on a webpage.

What Are “vw” and “vh”?

“vw” (Viewport Width): 1 “vw” equals 1% of the width of the browser’s viewport. If your viewport is 1000 pixels wide, 1 “vw” would equal 10 pixels.
“vh” (Viewport Height): 1 “vh” equals 1% of the height of the viewport. If your viewport is 800 pixels tall, 1 `vh` would equal 8 pixels.

These units are relative to the viewport, which is the visible area of a webpage. Unlike “px”, which is an absolute unit that remains static regardless of screen size, “vw” and “vh” adjust dynamically as the viewport changes.

Benefits of Using “vw” and “vh” Over “px”

1. Responsive Design:

When you use pixels (`px`) for sizing, your design becomes fixed. This means that as the screen size changes (from desktop to mobile, for instance), your elements may appear too large, too small, or misaligned. “vw” and “vh”, on the other hand, allow your layout to adapt to different screen sizes automatically, maintaining proportionate design elements that look good on any device.

For example:
“`css
/* With px */
.header {
height: 100px;
width: 600px;
}

/* With vw and vh */
.header {
height: 10vh;
width: 60vw;
}
“`
With “vw” and “vh”, the header’s dimensions will adjust proportionally, ensuring the design works on both a wide desktop monitor and a small mobile screen.

2. Viewport-Based Sizing:

Because “vw” and “vh” units are based on the browser’s viewport, developers can create layouts that scale based on the available screen real estate. This is particularly useful for full-screen components like hero banners, modals, and sliders, where maintaining the right proportions is crucial.

For instance, a full-screen background can be easily achieved using “vh”:
“`css
.full-screen-banner {
height: 100vh;
width: 100vw;
}
“`
This guarantees that the banner will always take up the entire screen, regardless of the device’s size or resolution.

3. Fluid Typography:

Fluid typography, where font sizes scale dynamically with the viewport size, is a growing trend in web design. By using `vw` for font sizes, you can ensure that text adjusts proportionally across different devices, improving readability and maintaining a consistent design aesthetic.

For example:
“`css
h1 {
font-size: 5vw;
}
“`
In this case, the heading text will be 5% of the viewport width, allowing larger fonts on more giant screens and smaller fonts on mobile devices without needing media queries.

4. No Media Query Overload:

One common problem with using `px` is that developers often need to write numerous media queries to handle different screen sizes. This can bloat your CSS file and make maintenance more difficult. By using “vw” and “vh”, you can reduce the need for excessive media queries, as the design elements naturally resize themselves according to the viewport.

5. Better Accessibility:

Using “vw” and “vh” can also improve accessibility. Since these units adjust based on the screen size, they can help ensure that elements like buttons, images, and text remain appropriately sized for users with visual impairments who may rely on zooming in or out.

6. Consistency Across Devices:

When using “px”, designs may look perfect on one device but completely different on another. This inconsistency can be frustrating, especially when ensuring a smooth user experience. With “vw” and “vh”, the relative sizes remain consistent, providing a more unified experience across multiple devices.

When Should You Still Use “px”?

While “vw” and “vh” offer many advantages, there are times when “px” might still be the better choice:
Pixel-perfect elements: Pixels can be useful if you need elements that remain a fixed size regardless of screen size (e.g., icons or small UI components).
Borders and fine-tuned design details: Pixels might offer more control for thin borders, margins, or padding, especially when small size differences matter.

Conclusion

Flexibility and adaptability are key to delivering excellent user experiences across different devices in modern web development. By opting for “vw” and “vh” units instead of “px,” you can create more responsive layouts, maintain design consistency, and require fewer adjustments via media queries. While “px” still has its place for some specific design elements, embracing relative units will ultimately result in cleaner, more scalable, and user-friendly designs.