markdownlint/doc/md009.md

# `MD009` - Trailing spaces

Tags: `whitespace`

Aliases: `no-trailing-spaces`

Parameters:

- `br_spaces`: Spaces for line break (`integer`, default `2`)
- `code_blocks`: Include code blocks (`boolean`, default `false`)
- `list_item_empty_lines`: Allow spaces for empty lines in list items
  (`boolean`, default `false`)
- `strict`: Include unnecessary breaks (`boolean`, default `false`)

Fixable: Some violations can be fixed by tooling

This rule is triggered on any lines that end with unexpected whitespace. To fix
this, remove the trailing space from the end of the line.

The `br_spaces` parameter allows an exception to this rule for a specific number
of trailing spaces, typically used to insert an explicit line break. The default
value allows 2 spaces to indicate a hard break (\<br> element). (You must set
`br_spaces` to a value >= 2 for this parameter to take effect. Setting
`br_spaces` to 1 behaves the same as 0, disallowing any trailing spaces.)

By default, trailing space is allowed in indented and fenced code blocks because
some programming languages require that. To report such instances, set the
`code_blocks` parameter to `true`.

By default, this rule will not trigger when the allowed number of spaces is
used, even when it doesn't create a hard break (for example, at the end of a
paragraph). To report such instances, set the `strict` parameter to `true`.

```markdown
Text text text
text[2 spaces]
```

Using spaces to indent blank lines inside a list item is usually not necessary,
but some parsers require it. Set the `list_item_empty_lines` parameter to `true`
to allow this (even when `strict` is `true`):

```markdown
- list item text
  [2 spaces]
  list item text
```

Rationale: Except when being used to create a line break, trailing whitespace
has no purpose and does not affect the rendering of content.