MD vs OPML
A detailed comparison of Markdown and OPML Outline — file size, quality, compatibility, and which format to choose for your workflow.
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Choosing between MD (Markdown, text/markdown) and OPML (OPML Outline, text/x-opml) depends on your target workflow, compression efficiency, and device support. Below is our side-by-side technical benchmark and instant bidirectional converter.
MD vs OPML at a glance
MD vs OPML| Dimension | .MD | .OPML |
|---|---|---|
| Format Name | Markdown (.md) | OPML Outline (.opml) |
| Format Family | Documents & Text | Documents & Text |
| Primary MIME | text/markdown | text/x-opml |
| Developer / Year | John Gruber & Aaron Swartz (2004) | Dave Winer (2000) |
| Pipeline Role | Read & Write | Read & Write |
When should you use MD vs OPML?
.MD Use when…
Use MD (Markdown) when your pipeline requires native text/markdown compatibility, predictable rendering, or specialized Documents & Text editing support.
.OPML Use when…
Use OPML (OPML Outline) when you need text/x-opml delivery, cross-platform Documents & Text distribution, or streamlined storage.
Technical Specifications
| Specification | .MD | .OPML |
|---|---|---|
| MIME type | text/markdown | text/x-opml |
| Extensions | .md, .markdown, .mdown, .mkd | — |
| Standard | CommonMark, GitHub Flavored Markdown (GFM) | OPML 2.0 (2006) |
| Encoding | UTF-8 (conventional) | — |
| Companion spec | RFC 7763 (2016) | — |
| Extension | — | .opml |
| Format | — | XML with nested <outline> elements |
| Primary use | — | RSS subscription interchange |
Strengths Comparison
.MD Strengths
- Readable as plain text even before rendering — fits in version control beautifully.
- Dead-simple: 90% of needs covered in 10 minutes of learning.
- Converts trivially to HTML, PDF, EPUB, and DOCX via Pandoc.
- Every modern IDE, note-taking app, and developer tool renders it natively.
- Lightweight — a typical Markdown file is kilobytes, not megabytes.
.OPML Strengths
- Standard RSS subscription interchange format.
- Simple XML — easy to parse and generate.
- Highly extensible via arbitrary attributes.
- Supported by every major outline and RSS tool.
Limitations
.MD — Limitations
- No formal authoritative spec — CommonMark, GFM, and MultiMarkdown differ on edge cases.
- Tables and complex layouts are clunky; footnotes and math require extensions.
- Links to images stay external — no embedded media unless you base64-inline.
- Styling is limited to what HTML allows — custom branding requires CSS outside Markdown.
.OPML — Limitations
- XML verbosity — larger than a JSON-based equivalent.
- Specification is loose — different tools disagree on edge cases.
- Primary use (RSS reading) has shrunk dramatically since Google Reader.
- No strong central stewardship.
Technical deep dive: MD vs OPML
Both MD and OPML serve distinct roles in modern digital pipelines. With KaijuConverter you can transcode between .md and .opml in seconds while preserving metadata and structural fidelity.
Frequently Asked Questions
MD (Markdown) uses MIME type text/markdown in the Documents & Text family, whereas OPML (OPML Outline) uses text/x-opml in the Documents & Text family. Each optimizes for different trade-offs in file size, fidelity, and software compatibility.
Yes. KaijuConverter uses tuned encoding profiles to preserve maximum visual, audio, or document fidelity when converting between MD and OPML.
Markdown is a lightweight text-based markup language created by John Gruber and Aaron Swartz in 2004. A .md file uses simple conventions (*italic*, **bold**, # headings, - lists) that compile to HTML. It became the default writing format for GitHub READMEs, Stack Overflow posts, Discord messages, and most developer documentation.
Markdown files are plain text — open in any text editor. For formatted preview use VS Code (built-in preview), Typora, Obsidian, or upload to GitHub/GitLab which render Markdown automatically. Every note-taking app (Notion, Bear, Joplin) handles Markdown natively.
Use KaijuConverter's Markdown-to-PDF converter, or command-line Pandoc (the gold standard — installed with one command, converts MD to PDF/HTML/DOCX/EPUB in a single line). VS Code with Markdown PDF extension also works locally.
Markdown for almost everything — it's 10× faster to write, version-control-friendly, and compiles to HTML automatically. Write raw HTML only when you need fine control over layout, embedded JavaScript, or features Markdown doesn't support (complex tables, forms). Static-site generators (Hugo, Astro, Jekyll) compile MD to HTML for you.
Markdown never had a formal spec for its first decade. CommonMark (2014) and GitHub Flavored Markdown (2017) standardized the core syntax, but edge cases (nested lists, HTML embedding, table syntax) still differ across renderers. For portability, stick to basic GFM features.
Yes — most modern doc tools are built on Markdown. MkDocs, Docusaurus, Astro Starlight, GitBook, and Read the Docs all accept Markdown input. For documentation needing rich features (tabs, callouts, versioning), MDX (Markdown + JSX components) extends MD with React-style embeds.
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