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register_taxonomy() WP 1.0

Creates or modifies a taxonomy object.

Note: Do not use before the 'init' hook.

A simple function for creating or modifying a taxonomy object based on the parameters given. If modifying an existing taxonomy object, note that the $object_type value from the original registration will be overwritten.

  • Global. Array. $wp_taxonomies Registered taxonomies.
  • Since 4.2.0 Introduced show_in_quick_edit argument.
  • Since 4.4.0 The show_ui argument is now enforced on the term editing screen.
  • Since 4.4.0 The public argument now controls whether the taxonomy can be queried on the front end.
  • Since 4.5.0 Introduced publicly_queryable argument.
  • Since 4.7.0 Introduced show_in_rest, 'rest_base' and 'rest_controller_class' arguments to register the Taxonomy in REST API.
  • Since 5.1.0 Introduced meta_box_sanitize_cb argument.
Works based on: WP_Taxonomy()
Hooks in function

WP_Error/null. WP_Error, if errors.


register_taxonomy( $taxonomy, $object_type, $args );
$taxonomy(string) (required)
Taxonomy key, must not exceed 32 characters.
$object_type(array/string) (required)
Object type or array of object types with which the taxonomy should be associated.

Array or query string of arguments for registering a taxonomy.

  • $labels (array)
    An array of labels for this taxonomy. By default, Tag labels are used for non-hierarchical taxonomies, and Category labels are used for hierarchical taxonomies. See accepted values in get_taxonomy_labels().
    Default: empty array

  • $description (string)
    A short descriptive summary of what the taxonomy is for.
    Default: ''

  • $public (true/false)
    Whether a taxonomy is intended for use publicly either via the admin interface or by front-end users. The default settings of $publicly_queryable, $show_ui, and $show_in_nav_menus are inherited from $public.

  • $publicly_queryable (true/false)
    Whether the taxonomy is publicly queryable. If not set, the default is inherited from $public

  • $hierarchical (true/false)
    Whether the taxonomy is hierarchical.
    Default: false

  • $show_ui (true/false)
    Whether to generate and allow a UI for managing terms in this taxonomy in the admin. If not set, the default is inherited from $public (default true).

  • $show_in_menu (true/false)
    Whether to show the taxonomy in the admin menu. If true, the taxonomy is shown as a submenu of the object type menu. If false, no menu is shown. $show_ui must be true. If not set.
    Default: inherited from $show_ui (default true)

  • $show_in_nav_menus (true/false)
    Makes this taxonomy available for selection in navigation menus. If not set, the default is inherited from $public (default true).

  • $show_in_rest (true/false)
    Whether to include the taxonomy in the REST API.

  • $rest_base (string)
    To change the base url of REST API route.
    Default: $taxonomy

  • $rest_controller_class (string)
    REST API Controller class name.
    Default: 'WP_REST_Terms_Controller'

  • $show_tagcloud (true/false)
    Whether to list the taxonomy in the Tag Cloud Widget controls. If not set, the default is inherited from $show_ui (default true).

  • $show_in_quick_edit (true/false)
    Whether to show the taxonomy in the quick/bulk edit panel. It not set, the default is inherited from $show_ui (default true).

  • $show_admin_column (true/false)
    Whether to display a column for the taxonomy on its post type listing screens.
    Default: false

  • $meta_box_cb (true/false/callable)
    Provide a callback function for the meta box display. If not set, post_categories_meta_box() is used for hierarchical taxonomies, and post_tags_meta_box() is used for non-hierarchical. If false, no meta box is shown.

  • $meta_box_sanitize_cb (callable)
    Callback function for sanitizing taxonomy data saved from a meta box. If no callback is defined, an appropriate one is determined based on the value of $meta_box_cb.

  • $capabilities (array)
    Array of capabilities for this taxonomy.

    • $manage_terms (string)
      Default 'manage_categories'.

    • $edit_terms (string)
      Default 'manage_categories'.

    • $delete_terms (string)
      Default 'manage_categories'.

    • $assign_terms (string)
      Default 'edit_posts'.
  • $rewrite (true/false/array)
    Triggers the handling of rewrites for this taxonomy. To prevent rewrite, set to false. To specify rewrite rules, an array can be passed with any of these keys:

    • $slug (string)
      Customize the permastruct slug.
      Default: $taxonomy key

    • $with_front (true/false)
      Should the permastruct be prepended with WP_Rewrite::$front.
      Default: true

    • $hierarchical (true/false)
      Either hierarchical rewrite tag or not.
      Default: false

    • $ep_mask (int)
      Assign an endpoint mask.
      Default: EP_NONE

    Default: true, using $taxonomy as slug

  • $query_var (string)
    Sets the query var key for this taxonomy. If false, a taxonomy cannot be loaded at ?{query_var}={term_slug}. If a string, the query ?{query_var}={term_slug} will be valid.
    Default: $taxonomy key

  • $update_count_callback (callable)
    Works much like a hook, in that it will be called when the count is updated. Default _update_generic_term_count() for taxonomies attached to other object types, such as users.
    Default: _update_post_term_count() for taxonomies attached to post types, which confirms that the objects are published before counting them

  • $_builtin (true/false)
    This taxonomy is a "built-in" taxonomy. INTERNAL USE ONLY! Default false.

Default: array()

Code of register taxonomy: wp-includes/taxonomy.php WP 5.2.1

function register_taxonomy( $taxonomy, $object_type, $args = array() ) {
	global $wp_taxonomies;

	if ( ! is_array( $wp_taxonomies ) ) {
		$wp_taxonomies = array();

	$args = wp_parse_args( $args );

	if ( empty( $taxonomy ) || strlen( $taxonomy ) > 32 ) {
		_doing_it_wrong( __FUNCTION__, __( 'Taxonomy names must be between 1 and 32 characters in length.' ), '4.2.0' );
		return new WP_Error( 'taxonomy_length_invalid', __( 'Taxonomy names must be between 1 and 32 characters in length.' ) );

	$taxonomy_object = new WP_Taxonomy( $taxonomy, $object_type, $args );

	$wp_taxonomies[ $taxonomy ] = $taxonomy_object;


	 * Fires after a taxonomy is registered.
	 * @since 3.3.0
	 * @param string       $taxonomy    Taxonomy slug.
	 * @param array|string $object_type Object type or array of object types.
	 * @param array        $args        Array of taxonomy registration arguments.
	do_action( 'registered_taxonomy', $taxonomy, $object_type, (array) $taxonomy_object );

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