I am trying & learning to build custom block for Gutenberg but spent a few hours on searching for full list of "available options". Maybe I was overlook...

Refer: Template and Block

For example, placeholder & align are options but what else?

function myplugin_register_book_post_type() {
    $args = array(
        'public' => true,
        'label'  => 'Books',
        'show_in_rest' => true,
        'template' => array(
            array( 'core/image', array(
                'align' => 'left',
            ) ),
            array( 'core/heading', array(
                'placeholder' => 'Add Author...',
            ) ),
            array( 'core/paragraph', array(
                'placeholder' => 'Add Description...',
            ) ),
    register_post_type( 'book', $args );
add_action( 'init', 'myplugin_register_book_post_type' );

Example 2: those empty array() should be allow to store some options, right?

$template = array(
    array( 'core/paragraph', array(
        'placeholder' => 'Add a root-level paragraph',
    array( 'core/columns', array(), array(
        array( 'core/column', array(), array(
            array( 'core/image', array() ),
        array( 'core/column', array(), array(
            array( 'core/paragraph', array(
                'placeholder' => 'Add a inner paragraph'

1 Answer 1


Option 1

Browse the block-library package in the Gutenberg's GitHub repository, and find the block metadata in a JSON file named block.json of the specific block. For example, for the core/image block, you can find the metadata (e.g. all available/supported attributes) here:


So basically, the URL format is:


where {name} is the block name without the core/ part.

Option 2 (PHP)

For blocks registered using the PHP/WordPress function register_block_type, you can use this to get the block attributes:

$block = WP_Block_Type_Registry::get_instance()->get_registered( 'core/latest-posts' );
$attrs = $block ? $block->get_attributes() : [];
var_dump( $attrs, $block );

Option 3 (JavaScript)

For blocks registered using the JavaScript function wp.blocks.registerBlockType, you can use this to get the block attributes:

var block = wp.blocks.getBlockType('core/gallery');
var attrs = block ? block.attributes : {};
console.log( attrs, block );
  • 4
    It’s a little bit annoying that after almost 1/2 year since publishing Gutenberg in WP, there documentation for it is still as bad... :( Commented Apr 24, 2019 at 4:43
  • 1
    wonderful answer and information! Detail and helpful, so glad to have you replied the question and wish it helps other as well.
    – kevinckc
    Commented Apr 24, 2019 at 4:44
  • 1
    @KrzysiekDróżdż, indeed.. :/ And the block.json is actually a new thing. In the previous Gutenberg releases, the block attributes are saved in blockAttributes but not in all block (the main index.js).
    – Sally CJ
    Commented Apr 24, 2019 at 4:54
  • @kevinckc, I hope so, too! And +1 for the helpful question. :)
    – Sally CJ
    Commented Apr 24, 2019 at 4:55

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