# Heading hierarchy

Canonical HTML: /atlas/heading-hierarchy
Atlas version: atlas-2026-07-28-v1
Category: Content structure for machines

## Definition

A heading hierarchy divides a document into named sections with an explicit information structure.

## How it works

A clear h1 followed by nested section headings helps readers and machines associate claims, examples, and caveats with the correct topic.

## How to validate it

Extract headings in source order, flag unexplained level jumps, and confirm that headings describe sections rather than decorative fragments.

## Common failure

Choosing heading levels only for font size creates a misleading outline even when the rendered page looks correct.

## Related topics

- [Semantic HTML](/atlas/semantic-html)
- [Data tables](/atlas/tables)