Markdown Frontmatter

parse.markdown(text) in JavaScript and parse_markdown in Pongo templates support optional frontmatter at the start of a Markdown string. Their return shapes differ: JavaScript also renders the body into an html field, while the Pongo filter keeps { content, frontmatter }.

Supported delimiters:

---   YAML
+++   TOML

Frontmatter is detected only when the first line is exactly --- or +++.

YAML Frontmatter

---
title: Hello
draft: false
tags:
  - guide
  - intro
---

# Hello

Body.

TOML Frontmatter

+++
title = "Hello"
draft = false
tags = ["guide", "intro"]

[meta]
author = "Veta"
+++

# Hello

Body.

Return Shape

const post = parse.markdown(files.readFile("content/posts/hello.md"));

{
  frontmatter: { title: "Hello", draft: false, tags: ["guide", "intro"] },
  content: "# Hello\n\nBody.\n",
  html: "<h1>Hello</h1>\n<p>Body.</p>\n"
}

content is the raw body, and html is the Markdown-rendered body. One blank line immediately after the closing delimiter is removed from content before html is rendered.

Files Without Frontmatter

# Plain Markdown

No frontmatter.

Returns:

{
  frontmatter: {},
  content: "# Plain Markdown\n\nNo frontmatter.\n",
  html: "<h1>Plain Markdown</h1>\n<p>No frontmatter.</p>\n"
}

Without frontmatter, content is the full input.

Pongo parse_markdown

The Pongo filter remains a frontmatter parser only:

{% set post = load_data("content/posts/hello.md")|parse_markdown %}
{{ post.content|markdown }}

It returns { content, frontmatter }; use the separate markdown filter to produce HTML.

Validation

Veta rejects:

• missing closing delimiters
• malformed YAML
• malformed TOML
• frontmatter that does not parse to an object
• multiple YAML documents
• non-finite numbers such as NaN or Inf
• maps with non-string keys

Parsed values are normalized into JavaScript-compatible values. Dates are exposed as strings.