# Task list items (extension)

GFM enables the tasklist extension, where an additional processing step is performed on list items.
A task list item is a list item where the first block in it is a paragraph which begins with a task list item marker and at least one whitespace character before any other content.
A task list item marker consists of an optional number of spaces, a left bracket ([), either a whitespace character or the letter x in either lowercase or uppercase, and then a right bracket (]).
When rendered, the task list item marker is replaced with a semantic checkbox element; in an HTML output, this would be an <input type="checkbox"> element.
If the character between the brackets is a whitespace character, the checkbox is unchecked. Otherwise, the checkbox is checked.
This spec does not define how the checkbox elements are interacted with: in practice, implementors are free to render the checkboxes as disabled or inmutable elements, or they may dynamically handle dynamic interactions (i.e. checking, unchecking) in the final rendered document.

- [ ] foo
- [x] bar

<ul>
<li><input disabled="" type="checkbox"> foo</li>
<li><input checked="" disabled="" type="checkbox"> bar</li>
</ul>

Task lists can be arbitrarily nested:

- [x] foo
  - [ ] bar
  - [x] baz
- [ ] bim

<ul>
<li><input checked="" disabled="" type="checkbox"> foo
<ul>
<li><input disabled="" type="checkbox"> bar</li>
<li><input checked="" disabled="" type="checkbox"> baz</li>
</ul>
</li>
<li><input disabled="" type="checkbox"> bim</li>
</ul>