Allows users to add custom CSS class names to blocks.

Source: wp-includes/block-supports/custom-classname.php
Since: 5.6.0

Support Key

supports.customClassName — defaults to true.

Registered Attribute

Functions

wp_register_custom_classname_support()

function wp_register_custom_classname_support( WP_Block_Type $block_type )

Since: 5.6.0
Access: private

Checks block_has_support( $block_type, 'customClassName', true ). Default is true, so most blocks get this attribute unless they explicitly opt out.

wp_apply_custom_classname_support()

function wp_apply_custom_classname_support( WP_Block_Type $block_type, array $block_attributes ): array

Since: 5.6.0
Access: private

Returns: Array with class set to the value of the className attribute, if present.

Registration

WP_Block_Supports::get_instance()->register(
    'custom-classname',
    array(
        'register_attribute' => 'wp_register_custom_classname_support',
        'apply'              => 'wp_apply_custom_classname_support',
    )
);