Comments on: Why The data: URI Scheme Could Help Save Your Slow Site

By: Drakim

Drakim — Thu, 27 Nov 2008 06:47:47 +0000

Also, Data URIs doesn’t cache like normal images. If you make a small small change to the CSS file which has a background image in the Data URI format, then the entire file, including the image, must be downloaded over again. This combined with the fact that base 64 encoding is very ineffective, can produce quite a slowdown to somebody with a slow internet connection.

Data URIs have their use, especially if you are writing a game in JavaScript, but for regular webpage optimizing, I recommend CSS sprites to reduce the number of http calls, not Data URIs. A plus side of this is that you don’t shut out 70% of the market (IE users).

By: Michael

Michael — Mon, 24 Nov 2008 01:45:51 +0000

Data URIs have some other performance related downsides. The data is base 64 encoded, and this makes the size a lot bigger. Your UI thread is going to be occupied parsing this large chunk of data. Most sites put their images on a separate domain, so the browser will download it in parallel to rendering the page.

By: Meitar

Meitar — Fri, 21 Nov 2008 11:35:44 +0000

@pavan_patil: URI schemes in general have the syntax you describe, yes, but the data: URI scheme doesn’t have any provision for an authority or path section. I think this is because those things are implied by virtue of the data being inline. So, for instance, when you access http://example.com/index.html and it contains an inlined image, then there’s no second HTTP request made, and thus no need to specify an authority or path because those are already known to be example.com and /index.html, respectively.

By: pavan_patil

pavan_patil — Fri, 21 Nov 2008 10:28:47 +0000

Thats True! But I wonder why no comment yet…! ITs my pleasure to comment first.
I think you have mis out something…. ! something about the feed
feedURI = ‘feed:’ absoluteURI | ‘feed://’ hier_part

the syntax for the ‘absoluteURI’ and ‘hier_part’ are defined in section 3 of [RFC2396]. A “feed” URI is basically the string ‘feed:’ or ‘feed://’ followed by a URI which when accessed over the network returns a representation of the data feed. If the “feed” URI string begins with the string ‘feed://’ then it MUST be followed by an authority with optional path and query string with the scheme for the URI for accessing the data feed being inferred as the “http” scheme. If the “feed” URI string begins with the string ‘feed:’ then it must be followed by an absolute URI which is the network accessible location of the data feed.

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