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What Is CSS Box Shadow?
The CSS box-shadow property adds shadow effects around an element's frame. It is one of the most widely used CSS properties for creating depth and visual hierarchy in web design. A single box-shadow declaration can include horizontal and vertical offsets, blur radius, spread radius, and color.
Box shadows can be layered — you can apply multiple shadows to a single element by separating them with commas. This technique enables sophisticated effects like realistic depth, glowing borders, and neumorphic designs. The inset keyword flips the shadow inside the element for pressed or recessed effects.
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Build a Box Shadow →When To Use Box Shadows
Box shadows are essential for creating depth and visual hierarchy in modern web interfaces. They guide the user's eye and communicate interactivity.
- Card and panel elevation — subtle shadows lift cards off the background to create a layered interface
- Button states — add or deepen shadows on hover to indicate interactivity and provide tactile feedback
- Modal and dropdown overlays — prominent shadows separate floating elements from the page below
Frequently Asked Questions
Does box-shadow affect layout or performance?
Box shadows do not affect layout — they are purely visual and do not change the element's size or position in the document flow. Performance is generally excellent in modern browsers, but very large blur radii or many layered shadows on frequently repainted elements can impact rendering speed.
Can I animate box-shadow?
Yes, box-shadow can be animated with CSS transitions and keyframes. However, animating box-shadow triggers repaints, which can be expensive. For smoother performance, consider animating opacity on a pseudo-element with a fixed shadow instead of transitioning the shadow values themselves.
What is the difference between box-shadow and drop-shadow?
box-shadow applies a rectangular shadow to the element's box (including its border-radius). filter: drop-shadow() applies a shadow that follows the element's actual shape, including transparent areas in images. Use box-shadow for UI elements and drop-shadow for images with transparency.