Do Modern Browsers Download Unused CSS Images?

Do Browsers Download Unused CSS Images?

In CSS, it's possible to specify images within CSS rules that may not be used by any elements in the page. For example:

.nothingHasThisClass {
  background: url(hugefile.png);
}

Does this mean that unused CSS images are still downloaded by the browser? The answer depends on the specific browser's implementation.

Browser-Dependent Behavior

A quick test across various browsers shows the following behavior:

• Chrome: Unused images aren't downloaded.
• Firefox: Unused images aren't downloaded.
• Safari: Unused images aren't downloaded.
• IE8: Unused images aren't downloaded.
• IE7: Unused images aren't downloaded.

However, the behavior of IE6 is unknown. If you have the ability to test IE6, please comment below with your findings.

Conclusion

Based on these tests, it appears that modern browsers generally don't download unused CSS images, reducing unnecessary network traffic and page load times.

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