I’ve been working on some feed support in MSDN’s new online platform (a beta of which is running http://msdn2.microsoft.com) and I had to decide what content-type to use when outputting a RSS feed. I knew this was a contentious issue in the past, but I thought it might have been resolved so I did some browsing of specs and discussions and ended up with the following links:

I’m sure I could find more, but it appears this was never really resolved… using application/xml seems the most ‘proper’, but the concern is that some browsers don’t know how to handle it … so the other choice is text/xml (specifically text/xml; charset=utf-8 or else the charset will default to US-ASCII). Hmm… which to choose? Even our own sites have multiple implementations:

Interestingly enough, I found one feed that used application/rss+xml (Sam’s RSS 2.0 feed) which I think is probably not the best choice since that content type was never officially registered, and it was the only feed I hit that IE didn’t understand (and therefore tried to just download).

I think I will go with “application/xml” which has the best features in my opinion.

  • It clearly indicates that this is not just text, so it should avoid issues with proxies messing with the characters,
  • it leaves the character set data in the xml declaration, avoiding a possible conflict if I specify one in the http headers that is different than what the feed specifies,
  • it displays correctly in IE and Firefox, and
  • it is consistent with what we are doing today with the MSDN main feed.

Now, what about those in-page links we have? <link rel="alternate" type="application/rss+xml" title="blah" href="rss.xml" /> …. perhaps they should be just “application/xml” as well?