Can you override CSS background image styles to ensure both images are loaded?

Question

Can you override CSS background image styles to ensure both images are loaded?

Suppose there are 2 CSS styles that assign background images to an element, and one style overrides the other. In this scenario, will both images be downloaded by the browser or just the overriding one?

I am asking this because I recently participated in a workshop on conditional stylesheets for mobile devices. If I replace my regular background images with smaller ones to conserve bandwidth, will the larger images still be loaded by the browser? The speaker seemed to suggest this would happen, but it seems counterintuitive to me.

html css

Answer 1

Answer №1

There are instances where the answer appears to be affirmative:

Answer 2

There are instances where the answer appears to be affirmative:

Answer 3

Answer №2

The replaced image will not load.

To clarify, take a look at this example: http://jsfiddle.net/thirtydot/MjKfG/1/show/

<div id="test">test</div>

div {
    background: url(http://dummyimage.com/600x400/000/fff)
}
#test {
    background: url(http://dummyimage.com/200);
    width: 200px;
    height: 200px
}

Only http://dummyimage.com/200 will be displayed.

This behavior is consistent across Chrome, Safari, Firefox, IE8/9, and Opera.

It's likely that all browsers follow this optimization as it is simple and effective.

Answer 4

The replaced image will not load.

To clarify, take a look at this example: http://jsfiddle.net/thirtydot/MjKfG/1/show/

<div id="test">test</div>

div {
    background: url(http://dummyimage.com/600x400/000/fff)
}
#test {
    background: url(http://dummyimage.com/200);
    width: 200px;
    height: 200px
}

Only http://dummyimage.com/200 will be displayed.

This behavior is consistent across Chrome, Safari, Firefox, IE8/9, and Opera.

It's likely that all browsers follow this optimization as it is simple and effective.

Answer 5

Answer №3

The response is negative. The initial style declaration where the background property was overridden will not be loaded. This occurs because browsers prioritize loading CSS files before other resources, processing them first before moving on to images based on order and overriding rules.

Here's an example:

div {
    border: solid 1px #000000;
    background: url('images/sprites.png') no-repeat x y;
}

.mobile div {
    border: solid 1px #000000;
    background: url('images/sprites_mobile.png') no-repeat x y;
}

Browsers interpret this CSS for mobile devices as follows:

div {
    border: solid 1px #000000;
    background: url('images/sprites_mobile.png') no-repeat x y;
}

As a result, browsers have already disregarded the attempt to load sprites_mobile.png.

Answer 6

The response is negative. The initial style declaration where the background property was overridden will not be loaded. This occurs because browsers prioritize loading CSS files before other resources, processing them first before moving on to images based on order and overriding rules.

Here's an example:

div {
    border: solid 1px #000000;
    background: url('images/sprites.png') no-repeat x y;
}

.mobile div {
    border: solid 1px #000000;
    background: url('images/sprites_mobile.png') no-repeat x y;
}

Browsers interpret this CSS for mobile devices as follows:

div {
    border: solid 1px #000000;
    background: url('images/sprites_mobile.png') no-repeat x y;
}

As a result, browsers have already disregarded the attempt to load sprites_mobile.png.

Answer 7

Answer №4

Have you considered conducting an experiment and analyzing the web log files to understand the situation better?

Alternatively, you could use a bit of PHP code to dynamically choose the right style sheets based on the user's device.

Answer 8

Have you considered conducting an experiment and analyzing the web log files to understand the situation better?

Alternatively, you could use a bit of PHP code to dynamically choose the right style sheets based on the user's device.

Can you override CSS background image styles to ensure both images are loaded?

Answer №1

Answer №2

Answer №3

Answer №4

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