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Markdown Frontmatter Patterns

Markdown Frontmatter Patterns Frontmatter is the YAML block at the top of a markdown file. It's where you encode everyth

Demo Author · · 1 min read ·
markdowncontenttooling

Markdown Frontmatter Patterns

Frontmatter is the YAML block at the top of a markdown file. It's where you encode everything the renderer needs to know that isn't prose.

The Baseline

---
title: My Post Title
date: 2026-03-08
tags: [foo, bar]
---
yaml

Almost every static site generator recognizes this shape.

Typed Frontmatter

Define a schema and validate on build:

import { z } from 'zod'

const PostSchema = z.object({
  title: z.string(),
  date: z.string().regex(/^\d{4}-\d{2}-\d{2}$/),
  tags: z.array(z.string()).default([]),
  draft: z.boolean().default(false),
})
ts

Fail the build on invalid frontmatter — catching a typo at build time beats a broken page in prod.

Computed Fields

Some fields shouldn't live in frontmatter because they're derivable: readingTime, excerpt, wordCount. Compute these from the body during the build pipeline.

Dates Are Strings

Always store dates as ISO strings, never native Date objects. YAML date parsing varies across toolchains, and strings serialize predictably to JSON.

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