# MD001 - Heading levels should only increment by one
Aliases: `heading-increment`
## What this rule does
Prevents skipping heading levels (like jumping from # to ### without ##).
## Why this matters
- **Document structure**: Logical heading hierarchy makes documents easier to navigate
- **Accessibility**: Screen readers rely on proper heading order to help users
- **Table of contents**: Automated TOC generators need correct heading levels
- **SEO**: Search engines use heading structure to understand content
## Examples
### ✅ Correct
```markdown
# Title
## Chapter 1
### Section 1.1
### Section 1.2
## Chapter 2
### Section 2.1
```
### ❌ Incorrect
```markdown
# Title
### Section 1.1 (skipped level 2)
##### Subsection (skipped levels 2, 3, and 4)
```
### 🔧 Fixed
```markdown
# Title
## Section 1.1
### Subsection
```
## Configuration
This rule has no configuration options.
## Automatic fixes
This rule automatically adjusts heading levels to maintain proper hierarchy, changing skipped levels to the next appropriate level.
## Learn more
- [Web Content Accessibility Guidelines - Headings](https://www.w3.org/WAI/tutorials/page-structure/headings/) - Why heading structure matters
- [CommonMark headings](https://spec.commonmark.org/0.31.2/#atx-headings) - Technical specification
## Related rules
- [MD002](md002.md) - First heading should be a top-level heading
- [MD003](md003.md) - Heading style should be consistent
- [MD022](md022.md) - Headings should be surrounded by blank lines