How to Achieve `background-size: cover` Functionality on HTML Elements with CSS?

How to Achieve Background-Size: Cover Functionality on HTML Elements with CSS

Simulating the functionality of background-size:cover on HTML elements like video or images can be a tricky task. However, using a combination of CSS properties, it's possible to create a solution that mimics the desired behavior without any scripting.

The CSS Solution

The key to achieving background-size:cover is to set the height, width, and minimum dimensions of the video element appropriately. By using calculated values based on the video's aspect ratio (e.g., 16:9), we can ensure that the video always scales to cover the available space while maintaining its aspect ratio.

<code class="css">.parent-element-to-video {
  overflow: hidden;
}

video {
  height: 100%;
  width: 177.77777778vh; /* 100 * 16 / 9 */
  min-width: 100%;
  min-height: 56.25vw; /* 100 * 9 / 16 */
}</code>

This CSS ensures that the video covers the entire parent element, regardless of its size.

Optional Centering

If desired, we can also center the video within the parent element using the following properties:

<code class="css">/* Merge with above CSS */
.parent-element-to-video {
  position: relative; /* or absolute or fixed */
}

video {
  position: absolute;
  left: 50%; /* % of surrounding element */
  top: 50%;
  transform: translate(-50%, -50%); /* % of current element */
}</code>

This approach works perfectly without any edge cases, offering a reliable solution for simulating background-size:cover on video elements. It's worth noting that the CSS3 properties used may not be compatible with older browsers, so script-based solutions may be necessary for full cross-browser compatibility.

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