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GlossaryProductsNew to AI

YAML frontmatter

YAML frontmatter is metadata at the start of a file, using key-value pairs, often for configuration or descriptions.

In plain terms

YAML frontmatter is a special section found at the very beginning of some files. It's used to store important details about the file itself, like its title, author, or other descriptive information.

This information is written in a format called YAML, which uses simple key-value pairs. For example, you might see a line like `title: My Awesome Document` or `version: 1.0`. This makes it easy for programs to read and understand the file's properties.

The expert version

YAML frontmatter is a block of metadata, typically enclosed by triple dashes (---), placed at the start of a document. It stores configuration or descriptive data as key-value pairs in YAML format. This is commonly used in static site generators, configuration files, and document processing pipelines to provide context or parameters for the content that follows.

Why it matters now

This term is appearing because Anthropic's documentation for creating custom Claude skills uses YAML frontmatter to define skill metadata. This highlights how structured metadata is becoming crucial for managing and deploying custom AI functionalities.

Where it shows up 1 items, newest first
How each company uses it
Anthropic Claude
Anthropic uses YAML frontmatter in its documentation for defining metadata related to custom AI skills for Claude.
Related terms

YAMLmetadataconfiguration filesstatic site generatorsClaudeAI skills

Often confused with
JSON
JSON is another data serialization format, but it uses curly braces and co
Markdown
Markdown is a lightweight markup language for formatting text, and whi
Origin

YAML frontmatter gained prominence with static site generators like Jekyll, which adopted it as a standard way to include metadata in content files. Source ↗

Try this about 5 minutes

You can see YAML frontmatter in action by looking at the source code of many websites built with static site generators. Many open-source projects host their documentation on platforms like GitHub, where you can view the raw files and find the metadata section at the top.

Try it: Playbook entries that use thisPlaybook →

The Playbook: reusable how-tos, prompts, configs and tips pulled out of the news.

Questions people ask

What is YAML?
YAML (YAML Ain't Markup Language) is a human-readable data serialization language often used for configuration files and data exchange between languages.
Where is YAML frontmatter used?
It's commonly used in static site generators, content management systems, and configuration files to provide metadata or settings for the content or application.

First seen on Subvolts Sep 3, 2026. Updated Sep 14, 2026. Written by an AI model from the items above and reviewed against them weekly; report an error.