frontmatter

 frontmatter  is a common way to include metadata in plain text. Currently the most seen method is including YAML in front of Markdown content, but some document formats offer built-in support for front matter.

Support

 * most static generators support a variety of front matter; this is most commonly YAML, but some accept TOML or JSON.
 * Github displays front matter in Markdown files in a table: Hugo example

asciidoc
asciidoc has a built-in support for metadata. While this metadata is usually minimal, it is OK to extend it with custom variables. It does not seem to support structured data, making it's use a little limited, but since it's part of the format, it's not as alien as the more common methods.

AsciiDoc User Guide

=
====== Stuart Rackham 
 * Author Initials: SJR
 * toc:
 * icons:
 * numbered:
 * website: http://asciidoc.org/

Jekyll
--- layout: post title: Blogging Like a Hacker permalink: https://domain.com/post category: Meta excerpt: Hello World! ---

Hugo
Hugo supports YAML, TOML, and JSON, but they need to be separated by different separators. This is a YAML example.

--- title: "spf13-vim 3.0 release and new website" description: "spf13-vim is a cross platform distribution of vim plugins and resources for Vim." tags: [ ".vimrc", "plugins", "spf13-vim", "vim" ] lastmod: 2015-12-23 date: "2012-04-06" categories: - "Development" - "VIM" slug: "spf13-vim-3-0-release-and-new-website" ---

Grav
--- title: Title of my Page slug: my-page-slug menu: My Page date: 01/01/2014 3:14pm published: true redirect: '/some/custom/route' template: custom taxonomy: category: blog tag: [sample, demo, grav] routes: default: '/my/example/page' canonical: '/canonical/url/alias' aliases: - '/some/other/route' - '/can-be-any-valid-slug' author: name: Sandy Johnson twitter: @sandyjohnson bio: Sandy is a freelance journalist and author of several publications on open source CMS platforms. ---

Pelican
Pelican is not following the usual method: it does not have the common separators.

reStructuredText
My super title


 * date: 2010-10-03 10:20
 * modified: 2010-10-04 18:40
 * tags: thats, awesome
 * category: yeah
 * slug: my-super-post
 * authors: Alexis Metaireau, Conan Doyle
 * summary: Short version for index and feeds

Markdown
Title: My super title Date: 2010-12-03 10:20 Modified: 2010-12-05 19:30 Category: Python Tags: pelican, publishing Slug: my-super-post Authors: Alexis Metaireau, Conan Doyle Summary: Short version for index and feeds

No common set of basic variables
None of the current static generators share the same keywords or syntax for even the most common variables, such as author, tags, publish date; with the exception of "title", though the case might vary here as well. (Title vs title ) - 2016-08-19 petermolnar

Most parsers are not aware of it
Since it's an alien format inside another format (YAML in Markdown most commonly ), therefore regular Markdown parsers are unaware of it and thus it will not be parsed accordingly. pandoc is an exception. - 2016-08-19 petermolnar