register_taxonomy( string $taxonomy, array|string $object_type, array|string $args = array() )

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.



(string) (Required) Taxonomy key, must not exceed 32 characters.


(array|string) (Required) Object type or array of object types with which the taxonomy should be associated.


(array|string) (Optional) 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().
  • 'description'
    (string) A short descriptive summary of what the taxonomy is for.
  • 'public'
    (bool) 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'
    (bool) Whether the taxonomy is publicly queryable. If not set, the default is inherited from $public
  • 'hierarchical'
    (bool) Whether the taxonomy is hierarchical. Default false.
  • 'show_ui'
    (bool) 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'
    (bool) 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 is inherited from $show_ui (default true).
  • 'show_in_nav_menus'
    (bool) Makes this taxonomy available for selection in navigation menus. If not set, the default is inherited from $public (default true).
  • 'show_in_rest'
    (bool) Whether to include the taxonomy in the REST API.
  • 'rest_base'
    (string) To change the base url of REST API route. Default is $taxonomy.
  • 'rest_controller_class'
    (string) REST API Controller class name. Default is 'WP_REST_Terms_Controller'.
  • 'show_tagcloud'
    (bool) 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'
    (bool) 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'
    (bool) Whether to display a column for the taxonomy on its post type listing screens. Default false.
  • 'meta_box_cb'
    (bool|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'
    (bool|array) Triggers the handling of rewrites for this taxonomy. Default true, using $taxonomy as slug. 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 $taxonomy key.
    • 'with_front'
      (bool) Should the permastruct be prepended with WP_Rewrite::$front. Default true.
    • 'hierarchical'
      (bool) Either hierarchical rewrite tag or not. Default false.
    • 'ep_mask'
      (int) Assign an endpoint mask. Default EP_NONE.
  • 'query_var'
    (string) Sets the query var key for this taxonomy. Default $taxonomy key. If false, a taxonomy cannot be loaded at ?{query_var}={term_slug}. If a string, the query ?{query_var}={term_slug} will be valid.
  • 'update_count_callback'
    (callable) Works much like a hook, in that it will be called when the count is updated. Default _update_post_term_count() for taxonomies attached to post types, which confirms that the objects are published before counting them. Default _update_generic_term_count() for taxonomies attached to other object types, such as users.
  • '_builtin'
    (bool) This taxonomy is a "built-in" taxonomy. INTERNAL USE ONLY! Default false.

Default value: array()


(WP_Error|void) WP_Error, if errors.


File: wp-includes/taxonomy.php

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 );


Version Description
5.1.0 Introduced meta_box_sanitize_cb argument.
4.7.0 Introduced show_in_rest, 'rest_base' and 'rest_controller_class' arguments to register the Taxonomy in REST API.
4.5.0 Introduced publicly_queryable argument.
4.4.0 The public argument now controls whether the taxonomy can be queried on the front end.
4.2.0 Introduced show_in_quick_edit argument.
2.3.0 Introduced.

© 2003–2019 WordPress Foundation
Licensed under the GNU GPLv2+ License.