MDS064: atx-heading-whitespace

ATX heading whitespace and indentation.

Flags malformed ATX headings. When the heading has content, checks that the opening hashes are followed by exactly one space (not a tab, not two spaces); empty headings (## with nothing after the hashes) are valid. Also checks that the heading starts at column 1, and that no closing hash sequence appears after the content. A trailing # run is only treated as a closing marker when preceded by whitespace; a # with no preceding space is kept as content.

# Config

Enable:

rules:
  atx-heading-whitespace: true

Disable:

rules:
  atx-heading-whitespace: false

# Examples

# Bad

Missing space after #:

#Heading

Multiple spaces after #:

#  Heading

Indented heading:

   # Heading

Closing # marker (any whitespace before #):

# Heading #

Multiple spaces before closing #:

# Heading  #

Tab after opening #:

#	Heading

# Good

# Heading

## Section

### Subsection

# Meta-Information

• ID: MDS064
• Name: atx-heading-whitespace
• Status: ready
• Default: enabled
• Fixable: yes
• Implementation: source
• Category: heading
• markdownlint:
  • MD018 (no-missing-space-atx)
  • MD019 (no-multiple-space-atx)
  • MD020 (no-missing-space-closed-atx) (partial)
  • MD021 (no-multiple-space-closed-atx)
  • MD023 (heading-start-left)
• rumdl:
  • MD018 (no-space-atx)
  • MD019 (multiple-space-atx)
  • MD020 (no-space-closed-atx) (partial)
  • MD021 (multiple-space-closed-atx)
  • MD023 (heading-start-left)
• mado:
  • MD018 (no-missing-space-atx)
  • MD019 (no-multiple-space-atx)
  • MD020 (no-missing-space-closed-atx) (partial)
  • MD021 (no-multiple-space-closed-atx)
  • MD023 (heading-start-left)
• obsidian-linter: headings-start-line (partial)