Some analysis has been done of feeds, and by far the most widely implemented is 0.91

But having said that, there are a couple of ways in which a large majority of these feeds break the 0.91 spec and use features that were included in 0.92.

  • Removing all limits. It’s common for feeds to contain more than 15 items and descriptions longer than 500 characters
  • HTML in description. It’s also common for the description field to include html but with character encoding so that it is still valid XML.
  • Since the Netscape DTD disappeared temporarily, it’s becoming common to just leave out the . Very few RSS parsers and readers were using it anyway, relying on the tag to identify the version.
  • A lot of feeds are missing the required element. This is no big deal as it is primarily a bit of advertising.

    So the most common format is really 0.91 and a half.