# MD023 - Start headings at the beginning of lines
Aliases: `heading-start-left`
## What this rule does
Checks that headings start at the beginning of the line without any indentation.
## Why this matters
- **Proper rendering**: Indented headings may not be recognized by all Markdown processors
- **Clear structure**: Headings at the line start make document hierarchy obvious
- **Consistency**: Uniform alignment creates a professional appearance
- **Avoid confusion**: Indented text with # symbols might be misinterpreted
## Examples
### ✅ Correct
```markdown
# Main Title
## Section Header
### Subsection
#### Detail Level
```
### ❌ Incorrect
```markdown
# Main Title
## Section Header
### Subsection
#### Detail Level
```
### 🔧 Fixed
```markdown
# Main Title
## Section Header
### Subsection
#### Detail Level
```
## Automatic fixes
This rule automatically removes any leading spaces or tabs from heading lines, moving them to the beginning of the line.
## Learn more
- [CommonMark specification for headings](https://spec.commonmark.org/0.31.2/#atx-headings)
- [Markdown heading best practices](https://www.markdownguide.org/basic-syntax/#headings)
## Related rules
- [MD001](md001.md): Use consistent heading levels
- [MD003](md003.md): Use consistent heading style
- [MD022](md022.md): Add blank lines around headings
- [MD026](md026.md): Remove trailing punctuation in headings