MD010 - Hard Tabs

Severity: Warning
Category: Whitespace
Auto-fix: ✓ Available

Rule Description

This rule checks for hard tab characters in the document and suggests replacing them with spaces for consistency.

Why This Rule Exists

Hard tabs can cause formatting inconsistencies:

Tab width varies between editors (2, 4, or 8 spaces)
Mixing tabs and spaces leads to misaligned text
Different markdown renderers may handle tabs differently
Code blocks and indentation become unpredictable

Examples

❌ Incorrect (violates rule)

→   This line starts with a tab
-→  List item with tab after marker
```→   Code block with tab indent

(Where → represents a tab character)

✅ Correct

    This line uses spaces for indentation
-   List item with spaces after marker
```    Code block with space indent

Configuration

[MD010]
code_blocks = true  # Check for tabs in code blocks (default: true)
spaces_per_tab = 4  # Number of spaces to replace each tab with (default: 4)

Automatic Fix

This rule supports automatic fixing with --fix. The fix will:

Replace each tab character with the configured number of spaces
Preserve the visual indentation of your content
Handle tabs in all contexts (text, lists, code blocks)

Apply Fix

# Fix all tab issues in your markdown files
mdbook-lint lint --fix docs/

# Preview what would be fixed
mdbook-lint lint --fix --dry-run docs/

When to Disable

Consider disabling this rule if:

Your project requires hard tabs (e.g., Makefiles in code examples)
You're working with legacy content that uses tabs consistently
Your team has standardized on tabs instead of spaces

Disable in Config

# .mdbook-lint.toml
disabled_rules = ["MD010"]

Disable Inline

<!-- mdbook-lint-disable MD010 -->
→   Content with tabs allowed here
<!-- mdbook-lint-enable MD010 -->

MD009 - No trailing spaces
MD012 - Multiple consecutive blank lines
MD047 - Files should end with newline

mdbook-lint Documentation