I saw a thread somewhere about why OPML was used as the export format for feed readers. Not sure I’ve ever written about this. At the time we were finishing up Radio UserLand, in either 2001 or 2002 (there were two big releases). I wanted a way to export the user’s feed list so people could use the same list in another reader. This one decision is why there are so many feed readers imho. Because we offered no lock-in as a key feature, everyone else including Google had to do it with their products. Users had the expectation of data portability, so it’s in the DNA of feed readers. Maybe we would have dominated the market with Radio if we didn’t export the feed list, it was for a while the only feed reader, but more likely Google would have entered and clobbered us, users wouldn’t have been able to use both products, or easily move on after Reader shut down. Anyway, why OPML? First, we had it around, it was new, I wanted people to use it, and I also wanted to use the outliner to edit my subscription lists. JSON didn’t exist as an option at the time. And using RSS for that seemed confusing and not right. RSS is a syndication format, representing a flow of information, where OPML represents a list that evolves, but each item has permanence. It’s static where RSS is dynamic. It’s like the difference between a podcast and an album of music. You listen to a podcast once and it’s gone, you may listen to an album many times over decades. Fundamentally different kinds of data, with different needs in how they evolve, and thus the format you use to represent it. Yes we could have shoehorned feed lists into RSS, but 20 years later I’m glad we didn’t. #