Outline Processor Markup Language

Filename extension .opml
Internet media type application/xml +, text/x-opml
Type Outline
File formats category - v  e   edit

OPML (Outline Processor Markup Language) is an XML format for outlines. Originally developed by Radio UserLand as a native file format for an outliner application, it has since been adopted for other uses, the most common being to exchange lists of web feeds between web feed aggregators.

The OPML specification defines an outline as a hierarchical, ordered list of arbitrary elements. The specification is fairly open which makes it suitable for many types of list data.


  • opml - This is the root element of the XML file.
    • version attribute - Required. This refers to the specification that must be used to read the file. Currently, these are 1.0, 1.1 and 2.0.
  • head - Required. Contains metadata for the file.
    • title - The title for the file.
    • dateCreated - The creation date and time of the file. This conforms to RFC 822.
    • dateModified - Date and time when the file was last modified.
    • ownerName - The owner of the file.
    • ownerEmail - The e-mail address of the owner.
    • ownerId (2.0) - The URL of the owner.
    • docs (2.0) - The URL for the version of the specification used.
    • expansionState - A comma-delimited list of numbers corresponding to line numbers that should be expanded on display.
    • vertScrollState - The line number that must be on the top of the list's window or viewport.
    • windowTop, windowLeft, windowRight, windowBottom - Specifies the offset of each edge of the window, if applicable, in pixels.
  • body - Body of the file, contains outline elements.
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