Clean and dedupe an OPML podcast list

Duplicate subscriptions in an OPML file almost always trace back to the same handful of causes. Re-exporting from an app you've used for years and merging that fresh file with an older backup you never fully deleted is the most common one by far. Another frequent cause is a feed URL change: when a podcast moves hosting providers, its RSS URL sometimes changes entirely while the show's title stays identical, so an app that dedupes strictly by feed URL will treat the old and new entries as two completely different shows even though they're really one podcast under a new address.

That's also exactly why title-based matching, while useful as a fallback, isn't foolproof on its own -- small formatting differences like trailing whitespace, stray punctuation, or a show renaming itself slightly between seasons will break an otherwise exact title match entirely. A cleanup pass that checks both the normalized feed URL and a normalized title catches meaningfully more real duplicates than either check would alone, which is why this tool runs both methods and clearly shows you which one flagged each specific match it found, so you can judge borderline cases yourself instead of trusting an automated merge blindly.

Before importing a cleaned file into a brand new app, it's worth spot-checking at least a few entries rather than trusting the automated pass blindly: confirm the duplicate you kept actually has a working xmlUrl attached to it, and don't simply assume the first entry listed in a group is automatically the right one to keep if that particular feed has since moved to a new host or address entirely without any redirect in place.

Entries missing a valid xmlUrl are excluded from the cleaned export entirely, since an outline without a working feed URL isn't a usable subscription in the destination app at all -- it's just dead weight carried forward from years of accumulated exports and re-imports. Once the list is genuinely clean, importing it into The Podcast App on either iOS or Android takes seconds, and the app's own duplicate handling on import adds one more layer of protection on top of whatever this tool already caught.