Markdown to HTML, as one self-contained file

What self-contained means

The usual result of turning markdown into HTML is a fragment: a block of tags that still needs a stylesheet, a font and often a script beside it before it looks like anything. That is fine when you are pasting it into a site you already run, and useless when what you wanted was the document. What comes out here is one file with all of it already inside — the markup, the styling, the drawn diagrams and formulas, everything it needs to look the way it looked on screen. There is no folder next to it, no assets directory, nothing to keep together. Double-click it and it opens in a browser, formatted, with no internet connection and nothing installed.

That property is the point of the file rather than a detail of it. Attach it to an email and the person opening it sees the document rather than a wall of tags. Put it on a memory stick, into a shared folder, or into an archive that has to still open in five years, and it does not rot when the site that was serving its stylesheet goes away. Hand it to somebody who has no markdown editor, or no editor at all, and they need nothing but a browser — which every machine already has. And because it is a single file it survives being forwarded, renamed and moved, which is what actually happens to documents.

Nothing is uploaded to make it. The markdown is read, formatted and packed into the one file inside your own browser, and no copy of your document is sent anywhere or held anywhere by anyone else — there is nobody on the other end to hold it. So a document you would not paste into a stranger's web form is a document you can turn into a file here.

Three steps

Get your document into the editor: open an .md file, drop one onto the page, or paste the text in. Read the formatted side and make any changes you want, because that is what the file will contain. Then choose Export, pick HTML (single file), and your browser saves it.