wp_kses() – Function | Developer.WordPress.org

Filters text content and strips out disallowed HTML.

Description

This function makes sure that only the allowed HTML element names, attribute names, attribute values, and HTML entities will occur in the given text string.

This function expects unslashed data.

Parameters

$contentstringrequired: Text content to filter.
$allowed_htmlarray[]|stringrequired: An array of allowed HTML elements and attributes, or a context name such as 'post'. See wp_kses_allowed_html() for the list of accepted context names.
$allowed_protocolsstring[]optional: Array of allowed URL protocols.
Defaults to the result of wp_allowed_protocols() .
Default:array()

Return

string Filtered content containing only the allowed HTML.

More Information

KSES is a recursive acronym which stands for “KSES Strips Evil Scripts”.

For parameter $allowed_protocols, the default allowed protocols are http, https, ftp, mailto, news, irc, gopher, nntp, feed, and telnet. This covers all common link protocols, except for javascript, which should not be allowed for untrusted users.

Source

function wp_kses( $content, $allowed_html, $allowed_protocols = array() ) {
	if ( empty( $allowed_protocols ) ) {
		$allowed_protocols = wp_allowed_protocols();
	}

	$content = wp_kses_no_null( $content, array( 'slash_zero' => 'keep' ) );
	$content = wp_kses_normalize_entities( $content );
	$content = wp_kses_hook( $content, $allowed_html, $allowed_protocols );

	return wp_kses_split( $content, $allowed_html, $allowed_protocols );
}

View all references View on Trac View on GitHub

Uses	Description
wp_kses_no_null()`wp-includes/kses.php`	Removes any invalid control characters in a text string.
wp_kses_normalize_entities()`wp-includes/kses.php`	Converts and fixes HTML entities.
wp_kses_hook()`wp-includes/kses.php`	You add any KSES hooks here.
wp_kses_split()`wp-includes/kses.php`	Searches for HTML tags, no matter how malformed.
wp_allowed_protocols()`wp-includes/functions.php`	Retrieves a list of protocols to allow in HTML attributes.

Used by	Description
wp_trigger_error()`wp-includes/functions.php`	Generates a user-level error/warning/notice/deprecation message.
WP_Site_Health::get_test_persistent_object_cache()`wp-admin/includes/class-wp-site-health.php`	Tests if the site uses persistent object cache and recommends to use it if not.
Walker_Comment::filter_comment_text()`wp-includes/class-walker-comment.php`	Filters the comment text.
filter_block_kses_value()`wp-includes/blocks.php`	Filters and sanitizes a parsed block attribute value to remove non-allowable HTML.
WP_Site_Health::get_test_sql_server()`wp-admin/includes/class-wp-site-health.php`	Tests if the SQL server is up to date.
wp_privacy_generate_personal_data_export_group_html()`wp-admin/includes/privacy-tools.php`	Generate a single group for the personal data export report.
WP_Customize_Manager::handle_load_themes_request()`wp-includes/class-wp-customize-manager.php`	Loads themes into the theme browsing/installation UI.
wp_filter_oembed_result()`wp-includes/embed.php`	Filters the given oEmbed HTML.
Automatic_Upgrader_Skin::feedback()`wp-admin/includes/class-automatic-upgrader-skin.php`	Stores a message about the upgrade.
WP_Theme_Install_List_Table::install_theme_info()`wp-admin/includes/class-wp-theme-install-list-table.php`	Prints the info for a theme (to be used in the theme installer modal).
WP_Theme_Install_List_Table::single_row()`wp-admin/includes/class-wp-theme-install-list-table.php`	Prints a theme from the WordPress.org API.
wp_plugin_update_row()`wp-admin/includes/update.php`	Displays update information for a plugin.
install_plugin_information()`wp-admin/includes/plugin-install.php`	Displays plugin information in dialog box form.
_get_plugin_data_markup_translate()`wp-admin/includes/plugin.php`	Sanitizes plugin data, optionally adds markup, optionally translates.
WP_Plugin_Install_List_Table::display_rows()`wp-admin/includes/class-wp-plugin-install-list-table.php`	Generates the list table rows.
wp_ajax_query_themes()`wp-admin/includes/ajax-actions.php`	Handles getting themes from themes_api() via AJAX.
wp_kses_data()`wp-includes/kses.php`	Sanitize content with allowed HTML KSES rules.
wp_filter_post_kses()`wp-includes/kses.php`	Sanitizes content for allowed HTML tags for post content.
wp_kses_post()`wp-includes/kses.php`	Sanitizes content for allowed HTML tags for post content.
wp_filter_nohtml_kses()`wp-includes/kses.php`	Strips all HTML from a text string.
wp_filter_kses()`wp-includes/kses.php`	Sanitize content with allowed HTML KSES rules.
WP_Theme::sanitize_header()`wp-includes/class-wp-theme.php`	Sanitizes a theme header.
wp_sidebar_description()`wp-includes/widgets.php`	Retrieve description for a sidebar.

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Changelog

Version	Description
1.0.0	Introduced.

User Contributed Notes

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Bart Kuijper 5 years ago

You must log in to vote on the helpfulness of this noteVote results for this note: 23You must log in to vote on the helpfulness of this note

Many function names in WordPress are self-explanatory and if they aren’t, their documentation usually sheds some light on how they got their name. I find this makes it easier to later recall their names and uses. However, wp_kses is an exception. So for anyone else wondering:

kses comes from the terms XSS (cross-site scripting) and access. It’s also a recursive acronym (every open-source project should have one!) for “kses strips evil scripts”.

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Codex 10 years ago

You must log in to vote on the helpfulness of this noteVote results for this note: 14You must log in to vote on the helpfulness of this note
Allowed HTML tags array
This is an example of how to format an array of allowed HTML tags and attributes.
```
array(
    'a' => array(
        'href' => array(),
        'title' => array()
    ),
    'br' => array(),
    'em' => array(),
    'strong' => array(),
);
```
- From what is shown in the core code, the attributes are typically set to true, rather than array(), so more like this: array( 'a' => array( 'href' => true, 'title' => true, ), 'br' => array(), 'em' => array(), 'strong' => array(), );
  
  nosilver4u 3 years ago
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Abdul Hadi 4 years ago

You must log in to vote on the helpfulness of this noteVote results for this note: 6You must log in to vote on the helpfulness of this note
WordPress wp_kses is an HTML filtering mechanism. If you need to escape your output in a specific (custom) way, wp_kses function in WordPress will come handy.
```
<?php
$str = 'Check Kses function I am <strong>stronger</strong> and cooler every single day <a href="#" rel="nofollow ugc">Click Here</a>';
echo $str;
$arr = array( 'br' => array(), 'p' => array(), 'strong' => array() );
echo 'String using wp_kses function....' . wp_kses( $str, $arr );
?>
```
Output:
Before wp_kses: Check Kses function I am stronger and cooler every single day Click Here
After wp_kses: String using wp_kses function…. Check Kses function I am stronger and cooler every single day Click Here

It will display a resultant string as shown in the output screen. It only reflects the allowed tags strong, br, p as defined in wp_kses function and anchor tag is removed. So, no link for click Here text is formed.
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J.D. Grimes 10 years ago

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See wp_kses_allowed_html() and /wp-includes/kses.php to get a list of the possible default values of the allowed HTML tags.

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TomS Caprice 3 years ago

// Allowed img tag and support svg base64 data like:  <img src="data:image/svg+xml;base64,__base64_code__" />
function wpdocs_allowed_html() {
	return array(
		'img' => array(
			'title' => array(),
			'src'	=> array(),
			'alt'	=> array(),
		)
	);
}

function wpdocs_allowed_protocols() {
	return array(
		'data' 	=> array(),
		'http'	=> array(),
		'https' => array(),
	);
}

function wpdocs_output_img() {
	$html = '';
	ob_start();
	?>

	<img src="data:image/svg+xml;base64,Your_base64_code" title="img_title" alt="alt_info" />

	<?php 
	$html = ob_get_contents();
	ob_end_clean();
	return $html;
}

$allowed_html      = wpdocs_allowed_html();
$allowed_protocols = wpdocs_allowed_protocols();
$wpdocs_img        = wpdocs_output_img();

echo wp_kses( $wpdocs_img, $allowed_html, $allowed_protocols )

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Rene Hermenau 2 years ago

You must log in to vote on the helpfulness of this noteVote results for this note: 1You must log in to vote on the helpfulness of this note
If you want to keep certain style properties you have to use another filter.
Unortunately wp_kses will check the style properties against a list of allowed properties and it will still strip the style attribute if none of the styles are safe.

E.g. Use this filter if you want to keep the `display` property within a `style`:
a
```
add_filter( 'safe_style_css', function( $styles ) {
    $styles[] = 'display';
    return $styles;
} );
```
Check kses.php for default:
https://core.trac.wordpress.org/browser/trunk/src/wp-includes/kses.php
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Mahdi Yazdani 2 years ago

Sanitize SVG markup for front-end display using wp_kses, and a list of allowed HTML elements and attributes specific to a SVG tag.

/**
* Sanitize SVG markup for front-end display.
*
* @param  string $svg SVG markup to sanitize.
* @return string 	  Sanitized markup.
*/
function prefix_sanitize_svg( $svg = '' ) {
	$allowed_html = [
		'svg'  => [
			'xmlns'       => [],
			'fill'        => [],
			'viewbox'     => [],
			'role'        => [],
			'aria-hidden' => [],
			'focusable'   => [],
			'height'      => [],
			'width'       => [],
		],
		'path' => [
			'd'    => [],
			'fill' => [],
		],
	];

	return wp_kses( $svg, $allowed_html );
}

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BigupJeff 1 year ago

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If you are using wp_kses to escape SVG, be warned `wp_kses() ` will strip camelcased attributes in your args. Make sure your args are converted to lowercase for their uppercase equivalents. For example:
```
$args = array(
	'svg'            => array(
		'viewbox'             => true, // viewBox
		'preserveaspectratio' => true, // preserveAspectRatio
	),
	'lineargradient' => array(             // linearGradient
		'gradientunits'     => true,   // gradientUnits
		'gradienttransform' => true,   // gradientTransform
		'spreadmethod'      => true,   // spreadMethod
	),
);
```
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Aurovrata Venet 1 year ago

You must log in to vote on the helpfulness of this noteVote results for this note: 0You must log in to vote on the helpfulness of this note
Allowed HTML elements attributes don’t need to be empty arrays, but simply a boolean,
```
array(
    'a' => array(
        'href' => true,
        'title' => true
    ),
    'br' => array(),
    'em' => array(),
    'strong' => array(),
);
```
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wp_kses( string $content, array[]|string $allowed_html, string[] $allowed_protocols = array() ): string

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