How do I stretch a background image to cover the entire HTML element?

Dealing with multiple backgrounds and screen resolutions

Layering and positioning of multiple backgrounds

In scenarios invloving multiple background images, CSS background property allows you to layer multiple images and specify each layer's position and size. The first image cited in your CSS is the topmost layer, with others stacked in order behind. Here's how you set multiple backgrounds:

.element {
  background-image: url('top-image.png'), url('bottom-image.jpg');
  background-position: center bottom, left top;
  background-size: cover, 50%;
  background-repeat: no-repeat, repeat;
}
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Handling high-resolution displays with media queries

Higher screen resolutions demand high-definition images for optimum visual fidelity. However, you must consider the impact of larger files on load times. You can handle this using media queries and image-set in your CSS, allowing the browser to select the right image based on display resolution:

.element {
  background-image: image-set(
    url('image-1x.jpg') 1x,
    url('image-2x.jpg') 2x,
    url('image-3x.jpg') 3x
  );
  background-size: cover;                  
  background-position: center;            
}
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And here's how you can use media queries for high-resolution screens:

@media only screen and (min-resolution: 2dppx) {
  .element {
    background-image: url('image-2x.jpg');
    /* Insert the \"Wow, that's HD!\" image here. */
  }
}
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Adjusting the background for responsiveness and performance

Adopting responsive design principles

For responsive design, your background-image needs to adapt to various screen sizes. Always try to use relative units for related properties, like background-position and background-size, to make your design fluid and adaptable.

Prioritizing performance

From a performance perspective, vector images (like SVGs) are generally smaller in file size and scale better than their raster counterparts. So be a savvy developer and prioritize your site performance. Use image compression tools to optimize your assets and keep in mind mobile users and their data constraints.

Cases and compatibility considerations

Tackling legacy browser support

For cross-browser compatibility, don't forget vendor prefixes and fall-backs for older browsers. Even though background-size: cover enjoys broad support, ensure you thoroughly test across different browsers, including mobile.

Averting disruption to the page layout

To avoid disrupting the page layout, always ensure your background image and the associated style considerations don't interfere with readability or push other elements out of sight due to adjustments in padding or margins.

Best practices for design and maintenance

Stay organized for easier CSS maintenance

When maintaining your CSS, good organization is the grease that keeps the coding wheels spinning. Use clear class names, keep your CSS tidy, and comment your code for future reference—especially when dealing with complex backgrounds or media queries.

Cautious utilization of external resources

When using external resources or code snippets, always consider their reliability. Keep local copies of your resources, trust only secure CDNs, and always check any third-party code for potential security breaches before integrating it into your project.