Width:100% vs. width:100vw: Understanding the Viewport Difference

When attempting to size elements to the screen height, you might encounter a dilemma between using "width:100%" and "width:100vw." Both approaches yield different results, raising the question: what's the fundamental distinction between these two units?

Viewport Width vs. 100%

The key difference lies in the nature of viewport units like "vw" and "vh." These units reference the dimensions of the viewport, which encompasses the entire visible screen. In contrast, "width:100%" aligns the element's size to the width of its parent container.

Understanding 100vw

If you set "width:100vw," the element's width will match the viewport's width precisely. However, this includes the document's margin, which can add extra space beyond the intended content area.

Achieving 100% Horizontal Fill

To make elements fill the entire horizontal screen, irrespective of margins, ensure that the body has no margin. Setting "body { margin: 0 }" will align the viewport width seamlessly with the full screen width.

Additional Benefits of Viewport Units

Beyond achieving precise screen sizing, viewport units offer several benefits:

• Responsive Design: Using "vw" for element dimensions makes websites inherently responsive, adapting to different screen sizes proportionally.
• Cross-Device Consistency: When you specify font sizes and element heights using "vw" or "vh," they scale consistently across devices, ensuring consistency regardless of resolution.
• Easy Scaling: Establishing "font-size: 1vw" in the body CSS allows you to scale all elements using rem units, making it effortless to port existing projects and frameworks to this responsive approach.