Markdown Front-matter Formatter & Validator

How it works

• This is the one tool in this family that only touches part of its input — Format re-serializes the YAML between the two --- lines with normalized indentation, and passes the Markdown body below the closing --- through byte-for-byte unchanged, blank lines and all.
• To JSON converts just the front-matter block’s data to JSON — the body isn’t included, since the point is checking what a post’s title, tags, or draft field actually resolves to, not converting the prose.
• Front-matter must start on the file’s very first line — a blank line or anything else before the opening --- means “no front-matter found,” the same position-based rule Jekyll, Hugo, and Astro content collections all use. A missing closing --- is a hard error, not treated as “the rest of the file is front-matter.”
• There’s no separate YAML parser here — the extracted block is handed straight to this site’s own YAML Formatter logic, so whatever it supports or rejects, this tool does too (block mappings/sequences, flow collections, literal block scalars — see its own page for the full scope).

Runs entirely in your browser — nothing you paste here is uploaded, logged, or stored.