Skip to main content

​
Syntax

turndownService.keep(filter)

​
Description

Determines which HTML elements should be kept as HTML in the Markdown output instead of being converted. By default, Turndown converts all recognized HTML to Markdown. Use this method to preserve specific elements as raw HTML.

​
Parameters

​
filter
string | array | function
required
Specifies which elements to keep as HTML:
  • String: A single tag name (e.g., 'del')
  • Array: Multiple tag names (e.g., ['del', 'ins'])
  • Function: Custom filter function (node, options) => boolean

​
Returns

​
instance
TurndownService
Returns the TurndownService instance for method chaining

​
Examples

​
Keep Single Element

turndownService.keep('del')
turndownService.turndown('<p>Hello <del>world</del></p>')
// Result: Hello <del>world</del>

​
Keep Multiple Elements

turndownService.keep(['del', 'ins'])
turndownService.turndown('<p>Hello <del>world</del><ins>World</ins></p>')
// Result: Hello <del>world</del><ins>World</ins>

​
Keep with Custom Filter

turndownService.keep(function (node) {
  return node.nodeName === 'SPAN' && node.getAttribute('class') === 'keep'
})

turndownService.turndown('<p>Convert <span>this</span> but not <span class="keep">this</span></p>')
// Result: Convert this but not <span class="keep">this</span>

​
Chaining Keep Calls

turndownService
  .keep('sub')
  .keep('sup')
  .turndown('<p>H<sub>2</sub>O and E=mc<sup>2</sup></p>')
// Result: H<sub>2</sub>O and E=mc<sup>2</sup>

​
Behavior Details

​
Block-Level Elements

Block-level elements that are kept will be separated from surrounding content by blank lines: 
turndownService.keep('div')
turndownService.turndown('<p>Before</p><div>Middle</div><p>After</p>')
// Result:
// Before
//
// <div>Middle</div>
//
// After

​
Inline Elements

Inline elements are kept without additional spacing: 
turndownService.keep('mark')
turndownService.turndown('<p>This is <mark>highlighted</mark> text</p>')
// Result: This is <mark>highlighted</mark> text

​
Notes

  • Returns the instance to enable method chaining
  • Can be called multiple times; newer filters take precedence
  • Keep filters are overridden by standard CommonMark rules and added rules
  • To keep elements handled by default rules, add a custom rule instead
  • The default keepReplacement function can be customized via constructor options
  • Block-level kept elements are wrapped with blank lines; inline elements are not

Build docs developers (and LLMs) love

Get started for freeTalk to us