fgmd

A f***ing good Markdown parser.

View the site at fgmd.dev, view the site's source at /site

• Standard. Passes all 652 CommonMark 0.31.2 spec examples and all 24 GFM extension examples.
• Safe by default. Raw HTML is shown as text unless you opt in, and only http, https, mailto, tel and relative URLs get through. Hostile input can't hang or crash it.
• Extensible. Eight built-in plugins, plus a plugin API for new inline syntax, block syntax and tree transforms.
• Zero runtime dependencies. The library uses no Node APIs, so it runs in Node, Deno and browsers. It has a first-class Svelte 5 component and a CLI for other languages.

Install

npm install @decbr/fgmd

Without Svelte

markdown() turns a string into HTML:

import { markdown, callouts, math } from '@decbr/fgmd';

markdown('# Hello *world*');
// '<h1>Hello <em>world</em></h1>\n'

markdown(source, {
  plugins: [callouts(), math()],
  headingIds: true,
  classes: { p: 'mb-4', a: 'text-accent' },
  linkAttrs: (url) => (url.startsWith('/') ? null : { target: '_blank', rel: 'noreferrer' })
});

For content anyone can write, such as comments, html: 'sanitize' lets through a safe, GitHub-like subset of HTML. markdownInline() renders a single line without the wrapping <p>.

A page's metadata can live in the file, in a --- block above the copy. frontmatter() splits it off:

import { frontmatter } from '@decbr/fgmd';

const { data, body } = frontmatter(source);
// data: { "title": "Page Title", "blurb": "Page Blurb" }, body: the Markdown after the block

markdown(source, { frontmatter: true }) renders the same file with the block left out. See Syntax.

Using React? See React.

From PHP, Python, Ruby or Go, use the CLI:

cat post.md | fgmd --plugins callouts,typography > post.html

With Svelte

Svelte 5 is an optional peer dependency. The <Markdown> component takes the same options as markdown(), and it renders real elements with no {@html}:

<script>
  import { Markdown } from '@decbr/fgmd/svelte';
  import { callouts } from '@decbr/fgmd';
  import source from './privacy.md?raw';
</script>

<Markdown {source} plugins={[callouts()]} classes={{ h2: 'text-2xl mt-10', p: 'mb-4 text-muted' }} />

<!-- short copy: inline markdown, no <p> -->
<p class="lede"><Markdown source={game.blurb} inline /></p>

With Vite, a .md file can be imported as a string:

<script>
    import Prose from '$lib/Prose.svelte';
    import privacy from './privacy.md?raw';
</script>

<Prose source={privacy} />

You can also draw any node your own way with a snippet. For that, and more, see Svelte.

Documentation

• Syntax: what's supported, and what changes when coming from a regex-based parser
• Options: every parsing and rendering option
• Plugins: the built-ins, and writing your own
• Safety: what the defaults protect against, and how html: 'sanitize' works
• Svelte: the component, snippets and props
• React: rendering in React and Next.js
• CLI: using fgmd from other languages (PHP, etc.)
• The tree: parsing to a tree, walking it and rendering it
• Recipes: option sets for common sites
• Development: tests, spec reports and regenerating data

License

MIT
decbr decbrks@pm.me