OPML: A standard format for exchanging web feeds
OPML (Outline Processor Markup Language) is an XML-based format commonly used for exchanging subscription lists for web feeds, especially podcasts and blogs. This article explains what OPML is, how it works, and why it's important for content aggregators and end users.
What is OPML?
OPML is a specialized XML structure designed for exchanging web feed metadata between web aggregators. It was invented by Dave Winer, one of the pioneers of weblog and podcasting technologies.
Main uses of OPML
- RSS Reader: Allows users to import and export their subscribed RSS feeds between different feed readers.
- Podcast Apps: Helps podcast listeners transfer their subscribed podcasts from one app to another.
- Content management systems: Supports the management of lists of related websites or resources.
Structure of an OPML file
- Head: Contains metadata about the file itself such as the title and creation date.
- Body: Contains the actual data, organized in a hierarchical structure of outline elements, each containing a link and optionally additional attributes such as type and category.
Advantages of using OPML
- Standardization: Provides a consistent method for exchanging information about subscriptions.
- Flexibility: Can be used for various data structures besides web feeds, such as task lists and project management data.
- Interoperability: Promotes collaboration and data flow between different systems and platforms.
Creating and editing OPML files
- Tools: Many RSS readers and podcast management apps offer the ability to directly export or import OPML files.
- Manual editing: Since they are XML, OPML files can also be edited in any text editor.
Challenges and considerations
- Privacy: Users should be careful when sharing OPML files, as they may contain personal information about their reading or listening habits.
- Compatibility: Not all applications support all elements defined in OPML, which can lead to data loss.
