ence

The block between two --- lines at the top of a file holds the page's settings. This page is the exact spec of what the parser (lib/frontmatter.js) accepts. Anything not listed here is not part of the supported subset — it produces a jprot check diagnostic, never a crash.

Structure

Copy---
key: value
---

• The block must start at the very first bytes of the file (^---).
• Closing --- may carry content immediately after (no blank line required).
• Lines are LF or CRLF; keys are case-sensitive.
• Lines that are blank or start with # are ignored.

Values

Syntax	Parses to	Example
plain text	string	title: About me
number	number	order: 1, level: 90.5
true / false	boolean	hidden: false
null / ~	null	cover: null
[a, b, c]	array	tags: [js, css]
"double"	string (escapes honoured)	title: "Say "hi""
'single'	string	desc: "It's fine"
empty	empty object {}	hero:

Colons inside a value are fine: time: 12:30:45, url: https://x.com/a:b. Date-like values stay strings (date: 2026-01-15 → "2026-01-15"), so comparisons like dateKey in the content graph handle them explicitly.

Maps and lists

Indentation (two spaces is conventional) nests maps and lists:

Copy---
hero:
  title: Hi
links:
  - github
  - x.com
sections:
  - component: Skills
    items:
      - name: JS
        level: 90
---

A key followed by deeper-indented lines opens a map; a - line opens a list item. A line dedented back to the key's level ends the map — later keys stay top-level:

Copy---
a:
  b: 1
c: 2   # top-level, not part of `a`
---

Block scalars

key: | collects every following deeper-indented line into one value, keeping line breaks. key: > folds the same lines into a single line. Chomping and width indicators (|-, >+, |2) are accepted; trailing newlines are clipped.

Copy---
hint: |
  First line
  Second line
summary: >
  One sentence
  folded into a line
---

Leading whitespace and blank lines inside a block are dropped (each line is trimmed before joining).

Diagnostics

jprot check reports, without failing the build:

• a missing closing --- delimiter
• a line that is not key: value
• a duplicate key (last value wins)

The parser never throws on any input — garbage yields a diagnostic, not a crash.

Not supported

• Flow YAML beyond one-line lists: {a: 1}, anchors, aliases, tags.
• Quoted keys containing colons ("my: key": 1).
• Multi-document files (only the first --- block is read).
• Block scalars with indentation preserved (content is trimmed).