MD018 - No missing space after hash in heading¶

Aliases: no-missing-space-atx

What this rule does¶

Ensures there's a space between the # symbols and the heading text.

Why this matters¶

• Readability: Headings without spaces look cramped and are harder to read
• Compatibility: Some Markdown processors won't recognize headings without spaces
• Standards: Proper spacing follows Markdown best practices

Examples¶

✅ Correct¶

# Heading 1
## Heading 2
### Heading 3
#### Heading 4
##### Heading 5
###### Heading 6

❌ Incorrect¶

#Heading 1
##Heading 2
###Heading 3
####Heading 4
#####Heading 5
######Heading 6

🔧 Fixed¶

# Heading 1
## Heading 2
### Heading 3
#### Heading 4
##### Heading 5
###### Heading 6

Configuration¶

This rule has no configuration options.

Special cases¶

This rule correctly handles:

• Emoji hashtags like #️⃣ and #⃣ (not treated as headings)
• Regular hashtags like #tag or #123 (not treated as headings)
• Only actual heading syntax triggers this rule

Automatic fixes¶

This rule automatically adds a space after the # symbols to properly format the heading.

Learn more¶

• CommonMark specification for headings - Technical details about heading syntax

Related rules¶

• MD019 - No multiple spaces after hash in heading
• MD020 - No missing space in closed heading
• MD021 - No multiple spaces in closed heading
• MD022 - Headings should be surrounded by blank lines