Editing OPML (section)

{{short description|XML format for outlines}}
{{one source|date=May 2017}}
{{Use dmy dates|date=July 2023}}
{{Infobox file format
| name = OPML
| icon = [[Image:Opml-icon.svg|100px]]
| extension = <code>.opml</code>
| mime = application/xml, text/xml, text/x-opml
| uniform_type = org.opml.opml
| conforms_to = public.xml
| developer = [[UserLand Software|UserLand]]
| creatorcode =
| genre = [[Outliner]]
| containerfor =
| containedby =
| extendedfrom = [[XML]]
| extendedto =
| url = {{URL|http://dev.opml.org/}}
}}

'''OPML''' ('''Outline Processor Markup Language''') is an [[XML]] format for [[Outline (list)|outlines]] (defined as "a tree, where each node contains a set of named attributes with string values"<ref name="Spec">{{cite web|url=http://dev.opml.org/spec2.html|title=OPML 2.0 Specification|access-date=18 March 2014}}</ref>). Originally developed by [[UserLand Software]] as a native file format for the [[outliner]] application in its [[Radio UserLand]] product, it has since been adopted for other uses, the most common being to exchange lists of [[web feeds]] between web [[feed aggregator]]s.<ref name="lifewire">{{Cite web |last=Fisher |first=Tim |date=2022-03-12 |title=How to Open, Edit, and Convert OPML Files |url=https://www.lifewire.com/opml-file-2622105 |access-date=2023-07-05 |website=[[Lifewire]]}}</ref>

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.

Support for importing and exporting [[RSS]] feed lists in OPML format is available in [[Mozilla Thunderbird]]<ref>{{cite web|access-date=2019-06-11|title=How to Subscribe to News Feeds and Blogs {{!}} Thunderbird Help|url=https://support.mozilla.org/en-US/kb/how-subscribe-news-feeds-and-blogs|website=support.mozilla.org}}</ref> and in most other RSS reader web sites and applications.<ref name="lifewire" />