Outline Processor Markup Language (.opml)
OPML, or Outline Processor Markup Language, is a file format utilized primarily for outlining data structures. Initially developed in 2000 by UserLand Software, OPML was designed to facilitate the exchange of outline-based information between different software applications. Its uses have expanded over time, notably in organizing RSS feed lists and managing hierarchical data. The OPML file extension denotes XML-based documents that offer simplicity and interoperability in transferring structured information across diverse platforms. In essence, OPML serves as a versatile tool in the realm of data organization and syndication.