css - Smallest data URI image possible for a transparent image

Question

I'm using a transparent 1x1 image with a background image, to be able to use sprites and still provide alternative text for some icons.

I want to use a data URI for the image to reduce the number of HTTP requests, but what would be the smallest possible string to produce a transparent image?

I realize I could use data URI:s for the actual images instead of sprites, but it's easier to maintain when everything is kept in the CSS instead of scattered around.

Answer 1

After playing around with different transparent GIFs, some are unstable and cause CSS glitches. For example, if you have an <img> and you use the tiniest transparent GIF possible, it works fine, however, if you then want your transparent GIF to have a background-image, then this is impossible. For some reason, some GIFs such as the following prevent CSS backgrounds (in some browsers).

Shorter (but unstable - 74 bytes)

data:image/gif;base64,R0lGODlhAQABAAAAACH5BAEKAAEALAAAAAABAAEAAAICTAEAOw==

I would advise using the slightly longer and more stable version as follows:

? Stable ? (but slightly longer - 78 bytes)

data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7

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As another tip, don't omit image/gif as one comment suggests. This will break in several browsers.