OPML (Outline Processor Markup Language) is the portable format every RSS reader supports for backing up and moving feed subscriptions. This tool round-trips OPML ↔ JSON ↔ URL list ↔ Markdown so you can edit a backup in plain text, migrate from Feedly to FreshRSS, or pull just the feed URLs out of a tangled categorised export.
OPML was created by Dave Winer in 2000 for outlining and quickly became the de facto interchange format for RSS reader subscription lists. The interesting attributes for feed exports are type="rss", text / title (display name), xmlUrl (the actual feed), and optionally htmlUrl (the site). Folders are just <outline> elements that wrap other outlines without an xmlUrl. This tool parses with DOMParser — the work is done locally and your subscription list is never uploaded.