When to consider base64 (DATA: URI) images?

Question

What are the factors that should trigger thinking about switching images over to Base64 embedded in CSS?

There seems to be a lot of generic pro/con type things out there

Answer 1

There are two different issues here:

1) base 64. Well there's no advantage here. The files are fatter than binary and are less likely to be cached. Resources should be in external files so they can be cached.

2) Sprites. CSS sprites are a technique where a single image is used instead of multiple ones. Portions of the image are "revealed" via CSS. These are more efficient because the number of network requests are greatly reduced. It's worth it.