[shod]

I'm usually eager to jump on board with recommendations from Stoyan’s performance calendar, but Anne’s description of baseline loading doesn't comport with my experience in Webkit browsers (and possibly others). They don't "display instantly after file download", but display almost line by line as the file is downloading, with a partial image appearing from top to bottom as information becomes available. Since this particular trick is about perception -- users being given some visual indication that that the image is loading, and data as soon as possible -- the difference between progressive and baseline loading seems like it should be subtler than the article suggests.

[aerobson]

I never said baseline jpegs display instantly after file download. They render as I describe several times, top to bottom or "chop chop chop." It's progressive jpegs that display instantly after file download IF the browser does not support progressive rendering of progressive jpegs.

The difference between the rendering of the two file types is not subtle.