OPML Viewer - View and Visualize OPML Files Online

The OPML Viewer is a free online tool that allows you to view and visualize OPML (Outline Processor Markup Language) files in a hierarchical, readable format. OPML is an XML-based format commonly used for exchanging feed lists, blogrolls, and other hierarchical data structures, especially in RSS feed readers and podcast applications. This viewer displays the structure of your OPML files in an easy-to-navigate tree format, making it simple to understand the organization of your feeds and outlines.

What is OPML?

OPML (Outline Processor Markup Language) is an XML format designed for representing outlines. It's widely used for:

RSS Feed Subscriptions: Exporting and importing feed lists between RSS readers
Podcast Subscriptions: Sharing podcast subscription lists
Blogrolls: Lists of blogs or websites
Hierarchical Data: Any tree-structured information
News Aggregators: Managing feed collections

OPML Structure

An OPML file typically contains:

Head Section: Metadata like title, dateCreated, dateModified
Body Section: Contains outline elements in a hierarchical structure
Outline Elements: Can have attributes like text, title, type, xmlUrl, htmlUrl, and nested child outlines

How to Use the OPML Viewer

Input OPML Data: Paste your OPML XML content into the input field, or upload an OPML file
Auto View: The viewer automatically parses and displays the structure as you type (with a 500ms delay)
Manual View: Click the "View" button for immediate parsing and display
Navigate Structure: Click the expand/collapse icons to navigate through the hierarchical outline structure
View Attributes: See all attributes for each outline element, including URLs, types, and descriptions

Key Features

Hierarchical Tree View: Visualize OPML structure in an expandable/collapsible tree format
Automatic Parsing: Real-time parsing as you type with debouncing
File Upload Support: Upload .opml or .xml files directly
Metadata Display: View all metadata from the OPML head section
Attribute Visibility: See all attributes for each outline element
Error Handling: Clear error messages for invalid OPML/XML
Sample Data: Load sample OPML to test the tool
Interactive Navigation: Expand and collapse nodes to explore the structure

OPML Viewing Process

The viewer processes OPML files as follows:

XML Parsing: Parses the OPML XML using the browser's DOMParser
Structure Extraction: Extracts the version, head, and body sections
Recursive Outline Parsing: Recursively processes all outline elements and their children
Tree Rendering: Displays the structure in a hierarchical tree format
Attribute Display: Shows all attributes for each outline element

Example OPML Structure

Here's an example of how OPML is displayed in the viewer:

OPML Input:

<opml version="2.0">
  <head>
    <title>My Feed Subscriptions</title>
    <dateCreated>Mon, 01 Jan 2024 12:00:00 GMT</dateCreated>
  </head>
  <body>
    <outline text="Technology">
      <outline type="rss" text="TechCrunch" xmlUrl="https://techcrunch.com/feed/" />
    </outline>
  </body>
</opml>

Viewer Display:

The viewer will display:

Metadata Section: Shows version, title, and dateCreated
Outlines Tree: Displays "Technology" as a parent node
Child Outlines: Shows "TechCrunch" as a child with its RSS feed URL
Attributes: Displays type="rss" and xmlUrl attributes

Use Cases

Feed Management: Visualize and understand your RSS feed subscriptions
Podcast Organization: View the structure of your podcast subscription lists
Data Analysis: Understand the hierarchical structure of OPML files
Debugging: Identify issues in OPML file structure
Documentation: Document and explain OPML file structures
Migration Planning: Review OPML structure before migrating between services
Quality Assurance: Verify OPML file structure and completeness

OPML Attributes

Common OPML outline attributes that are displayed in the viewer:

text: The display text for the outline
title: The title of the outline
type: The type of outline (e.g., "rss", "link")
xmlUrl: The XML/RSS feed URL
htmlUrl: The HTML URL of the feed source
description: Description of the outline
language: Language of the content

Tips for Using the OPML Viewer

Validate OPML: Ensure your OPML file is well-formed XML before viewing
Use File Upload: For large OPML files, use the file upload feature
Navigate Tree: Click expand/collapse icons to explore the structure
Check Attributes: Review all attributes to understand feed configurations
Sample Data: Use the sample data button to see an example structure

Common OPML Sources

RSS Readers: Feedly, NewsBlur, The Old Reader export OPML
Podcast Apps: Overcast, Pocket Casts, Apple Podcasts support OPML
Blogrolls: WordPress and other platforms export blogrolls as OPML
Feed Aggregators: Many feed aggregation services use OPML

Benefits of Using the OPML Viewer

Viewing OPML files provides several advantages:

Visual Understanding: See the hierarchical structure at a glance
Easy Navigation: Expand and collapse nodes to explore the structure
Attribute Inspection: View all attributes without editing the XML
Error Detection: Identify structural issues in OPML files
Documentation: Understand OPML structure for documentation purposes
No Installation: Works directly in your browser without any software
Privacy: All processing happens locally in your browser

Frequently Asked Questions

What is the difference between OPML Viewer and OPML to JSON Converter?

The OPML Viewer displays OPML files in a hierarchical tree format, making it easy to visualize and navigate the structure. The OPML to JSON Converter transforms OPML files into JSON format for use in applications and APIs. Use the viewer when you want to understand the structure, and use the converter when you need to transform the data format.

Can I edit OPML files with this viewer?

No, this tool is a viewer only. It displays the OPML structure in a readable format but does not allow editing. For editing OPML files, you would need to modify the XML source directly or use a dedicated OPML editor.

Does the viewer preserve all OPML attributes?

Yes, the viewer displays all attributes from OPML outline elements, including text, title, type, xmlUrl, htmlUrl, description, and any custom attributes. All attributes are shown in the tree view for each outline element.

Can I upload OPML files?

Yes, you can use the file upload button in the input field to upload .opml or .xml files directly. The viewer will parse the file content and display the structure automatically.

How are nested outlines displayed?

Nested outlines are displayed in a hierarchical tree structure. Parent outlines can be expanded or collapsed to show or hide their child outlines. The tree view uses indentation and connecting lines to show the parent-child relationships clearly.

What if my OPML file has errors?

If your OPML file has XML syntax errors or is malformed, the viewer will display a clear error message indicating what went wrong. Make sure your OPML file is valid XML and follows the OPML specification.

Can I use this viewer for RSS feed migration?

Yes, this tool is perfect for understanding your RSS feed structure before migration. You can view your OPML file to see all your subscriptions, their organization, and attributes, which helps in planning the migration to a new RSS reader or service.

Is my OPML data stored or sent to a server?

No, all processing happens locally in your browser. Your OPML data is never sent to any server, ensuring complete privacy and security of your feed subscriptions and data.