wp-includes/post.php:20Creates the initial post types when 'init' action is fired.
function create_initial_post_types() { WP_Post_Type::reset_default_labels(); register_post_type( 'post', array( 'labels' => array( 'name_admin_bar' => _x( 'Post', 'add new from admin bar' ), ), 'public' => true, '_builtin' => true, /* internal use only. don't use this when registering your own post type. */ '_edit_link' => 'post.php?post=%d', /* internal use only. don't use this when registering your own post type. */ 'capability_type' => 'post', 'map_meta_cap' => true, 'menu_position' => 5, 'menu_icon' => 'dashicons-admin-post', 'hierarchical' => false, 'rewrite' => false, 'query_var' => false, 'delete_with_user' => true, 'supports' => array( 'title', 'editor' => array( 'notes' => true ), 'author', 'thumbnail', 'excerpt', 'trackbacks', 'custom-fields', 'comments', 'revisions', 'post-formats', ), 'show_in_rest' => true, 'rest_base' => 'posts', 'rest_controller_class' => 'WP_REST_Posts_Controller', ) ); register_post_type( 'page', array( 'labels' => array( 'name_admin_bar' => _x( 'Page', 'add new from admin bar' ), ), 'public' => true, 'publicly_queryable' => false, '_builtin' => true, /* internal use only. don't use this when registering your own post type. */ '_edit_link' => 'post.php?post=%d', /* internal use only. don't use this when registering your own post type. */ 'capability_type' => 'page', 'map_meta_cap' => true, 'menu_position' => 20, 'menu_icon' => 'dashicons-admin-page', 'hierarchical' => true, 'rewrite' => false, 'query_var' => false, 'delete_with_user' => true, 'supports' => array( 'title', 'editor' => array( 'notes' => true ), 'author', 'thumbnail', 'page-attributes', 'custom-fields', 'comments', 'revisions', ), 'show_in_rest' => true, 'rest_base' => 'pages', 'rest_controller_class' => 'WP_REST_Posts_Controller', ) ); register_post_type( 'attachment', array( 'labels' => array( 'name' => _x( 'Media', 'post type general name' ), 'name_admin_bar' => _x( 'Media', 'add new from admin bar' ), 'add_new' => __( 'Add Media File' ), 'add_new_item' => __( 'Add Media File' ),Introduced in 2.9.0. Unchanged from 6.7.7 through 7.1.0.
Signature, return type and hooks compared across 5 parsed releases.
src/wp-includes/post.php, and regenerated for each WordPress release so it tracks the code rather than a snapshot of it.