Outline Processor Markup Language File
In order to exchange outline structured information the OPML file format was created, this is a format based on XML and makes it possible to exchange information between various operating systems and system environments. These files are known as Outline Processor Markup Language Files which have the .opml file extension.
» OPML Editor
How to open .opml files?
Software to open .opml files
What are .opml files