Haddock to OPML Converter
Processing entirely on your device — large files may take a moment.
Convert OPML outlines into Markdown or Word documents, or turn bullet lists back into an importable outline. If your files are still in Haddock format, this page is the shortcut: Haddock is the documentation markup of the Haskell ecosystem: -- comment blocks attached to functions, rendered into the API docs every Hackage package ships.
This converter runs entirely in your browser using WebAssembly — your files never leave your device, nothing is uploaded, and there are no watermarks, sign-ups or queues. Drop in several files at once to convert them as a batch.
How Haddock compares to OPML
| Haddock | OPML | |
|---|---|---|
| Structure | Comment markup (--, 'links', @mono@) | XML <outline> tree |
| Types / schema | UTF-8 text | XML, text + attributes |
| Compatibility | Haskell, Hackage, Pandoc | RSS readers, outliners, Pandoc |
| Best for | Haskell API documentation | Subscriptions lists and mind maps |
How to convert Haddock to OPML
- 1
Select your files
Select your Haddock file.
- 2
Convert instantly
The file is first converted to markdown (an interchange format that keeps headings, lists and paragraphs), then rebuilt into the target format.
- 3
Download results
Download the OPML — structure preserved, heavy layout simplified.
About the Haddock format
Haddock is how Haskell explains itself: documentation comments in -- blocks, marked up with 'links' to identifiers, @monospace@ and /italics/, compiled into the API reference pages every package on Hackage publishes. The markup lives inside source files, but the format is its own small language.
Converted out of source comments, Haddock text becomes ordinary structured prose: Pandoc maps headings, code blocks and identifier links onto Markdown or HTML, so API knowledge can move into handbooks, wikis or static-site generators without retyping.
+Strengths
- ✓Documents live next to the code they describe
- ✓Identifier-aware linking across the API
- ✓Standard for the entire Haskell ecosystem
!Limitations
- −Meaningful only inside Haskell projects
- −Small grammar, few writers outside Haddock itself
- −Embedded in comments — needs extraction first
About the OPML format
OPML (Outline Processor Markup) is XML for hierarchies: nested <outline> elements, each with text and optional attributes. It is the silent standard behind podcast and RSS subscription lists — every "export subscriptions" button produces one — and the interchange format for outliners like Workflowy, Dynalist and OmniOutliner.
An outline is already half a document: Pandoc turns OPML hierarchies into Markdown headings, Word outlines or HTML pages with the nesting preserved, and can write OPML back out so a bulleted plan becomes an importable tree in your outliner of choice.
+Strengths
- ✓Universal outline exchange between outliners
- ✓The RSS/podcast subscription standard
- ✓Trivially parseable XML
!Limitations
- −Hierarchies only — no rich text per node
- −Attribute conventions vary between apps
- −Rarely rendered directly for humans
Why convert Haddock to OPML?
Converting makes sense where the strengths of OPML meet what Haddock cannot give you. Universal outline exchange between outliners Meanwhile Meaningful only inside Haskell projects One pass through the converter above puts your file on the right side of that trade-off.
Frequently asked questions
Is this Haddock to OPML converter really free?
Yes — completely free, with no sign-up, no watermark and no daily conversion limits. The site is supported by advertising.
Are my files uploaded to a server?
No. The conversion runs entirely inside your browser using WebAssembly, so your files never leave your device — that is what makes it instant and private.
Does it work on Windows, Mac, iPhone and Android?
Yes. Anything with a modern browser works: Windows, macOS, Linux, Android and iOS. No software installation is required.
Is there a file size limit for Haddock to OPML?
The only limit is your device's memory, since nothing is uploaded. Files up to a few hundred megabytes work fine on a modern desktop browser; very large files simply take a little longer.
Will the layout of my Haddock file be preserved exactly?
This converter renders your Haddock content into OPML with pages, proportions and images kept as close to the original as the target format allows. Use the preview before downloading to confirm it looks the way you expect.
Can I edit the OPML result afterwards?
That depends on the target: OPML is designed for what it does, and this converter reproduces its content faithfully rather than inventing editable structure. For heavy re-editing, work from a format built for editing and export the final version here.