What is Meltdown?
Meltdown is a profile language for Markdown documents. A profile recognizes roles in ordinary Markdown blocks, then applies presentation rules for rendering and export.
Markdown documents, profile-driven presentation
Meltdown separates what a document says from how a document presents itself.
Authors keep writing ordinary Markdown. A Meltdown profile recognizes roles in that source and renders the same text as letters, official acts, manual pages, parliamentary papers, or encyclopedic articles.
Markdown
# Document
26 April 2026
Plain text stays plain.
Meltdown profile
roles:
DateLine:
where:
- matches date
layout:
DateLine:
style: Meta
Rendered document
Document
26 April 2026
Plain text stays plain.
What is Meltdown?
A recognition and presentation layer for Markdown.
Meltdown is to Markdown what CSS is to HTML, with one extra move: before styling, it can recognize the structural role of each Markdown block. A paragraph can become a date line, a recipient address, a recital, a section heading, a citation, or plain body text without adding classes or custom syntax to the Markdown.
The profile remains separate from the document. That makes the same authoring format useful across families of documents where consistent presentation matters.
FAQ
Plain answers about what Meltdown is and is not.
Meltdown is still a work in progress. The RFC is a draft, and the word currently names both the proposed standard and this small browser implementation of it.
What can you do with Meltdown?
You can keep source text simple while rendering it as a specific kind of document: a policy letter, legal act, manual page, parliamentary paper, or article.
Is Meltdown something like Markdown?
It sits next to Markdown rather than replacing it. Markdown carries the words and basic structure; Meltdown adds recognition, layout, styling, and export behavior.
Is this LaTeX in disguise?
No. It shares LaTeX's concern for repeatable document presentation, but the goal is different: keep authors in plain Markdown and move formatting decisions into reusable profiles.
How is this useful?
It is useful when many documents follow a recognizable pattern and need consistent presentation without adding custom markup to every source file.
When is it not useful?
It is probably overkill for one-off prose, highly designed pages, or documents where the source already carries all the semantic structure you need.
Is Meltdown open source?
Yes. This implementation is published as CC-0. The implementation work was done with help from GPT 5.5 and other large language models.
Is the RFC final?
No. The RFC is a draft and the implementation is experimental. The demos are meant to make the idea concrete while the standard and vocabulary are still settling.
Demonstrations
One idea, several document families.
The playground is now just one flexible tool among the demos. The other examples show more specific readers and document workflows built on the same core pipeline.
Abstract tool
Playground
Edit Markdown, edit a Meltdown profile, compare the normal Markdown render with the role-aware document render, and export the result.
Parliamentary papers
Bundestag Drucksachen
Browse a corpus of Bundestag documents and compare Markdown, Meltdown output, and PDF render views.
Legal drafting
Delegated Act
Render an Article 25 CRA draft as an Official Journal-style document from plain Markdown source.
Reference manuals
newos man
Apply one manual-page profile across a large set of Markdown command references.
Encyclopedic articles
Wikipedia Markdown Reader
Convert live Wikipedia articles to Markdown, then render them with Meltdown figures, citations, and article structure.
Shared core