WooCommerce Blocks Development

Before writing code

Fetch live docs:

1. Web-search site:developer.woocommerce.com blocks extensibility for blocks extension docs
2. Fetch https://developer.wordpress.org/block-editor/ for Block Editor handbook
3. Web-search woocommerce checkout blocks extension api for checkout extension patterns

Architecture Overview

What WooCommerce Blocks Are

React-based blocks for the WordPress block editor (Gutenberg):

• Cart Block — replaces [woocommerce_cart] shortcode
• Checkout Block — replaces [woocommerce_checkout] shortcode (default since WC 8.3)
• Product Blocks — grids, filters, search, featured products
• Mini Cart Block — header cart widget

Store API

A dedicated REST API powering the block-based cart and checkout:

• Base: /wp-json/wc/store/v1/
• Endpoints: cart, cart/items, checkout, products, batch
• Nonce-authenticated (no API keys needed — runs in the customer's session)
• Separate from the WooCommerce REST API v3 (which is admin-facing)

Key Packages

Extending Checkout Blocks

Integration Points

The block-based checkout provides extension points:

• Inner Blocks — add custom blocks within checkout layout
• Slot Fills — inject content into predefined areas (before/after payment, shipping, etc.)
• Filters — modify text, labels, and data displayed in checkout
• Store API extensions — add custom data to cart/checkout API responses

Checkout Extension API (PHP Side)

Use ExtendSchema and StoreApi classes to:

1. Extend the Store API response with custom data
2. Add custom endpoint data to cart items, shipping, or checkout
3. Process custom data during checkout via ExtendSchema::register_endpoint_data()

Checkout Extension API (JS Side)

Use @woocommerce/blocks-checkout exports:

• registerCheckoutFilters — modify displayed values (item names, prices, subtotals)
• ExperimentalOrderMeta — slot for adding custom order meta display
• ExperimentalDiscountsMeta — slot for custom discount display

Registering a Checkout Block

1. Register the block server-side with register_block_type()
2. Declare the block as a checkout inner block via BlockRegistry
3. Provide edit and save React components
4. Enqueue scripts for the frontend and editor

Building Custom Product Blocks

Block Registration

Register with register_block_type():

• block.json — metadata file defining name, attributes, supports, editor/frontend scripts
• edit.js — editor component
• save.js — save component (or null for dynamic)
• render.php — server-side rendering for dynamic blocks

Server-Side Rendering

Use dynamic blocks with render_callback or render.php for product data:

• Access WooCommerce data via PHP (products, cart, etc.)
• Return HTML string from the render function
• Preferred for data-dependent blocks

Store API Extension

Adding Custom Data to Cart/Checkout

Register custom data via woocommerce_blocks_loaded action:

• Use Automattic\WooCommerce\StoreApi\Schemas\ExtendSchema
• Define namespace, schema, and data callback
• Data appears in Store API responses under extensions.{namespace}

Processing Custom Checkout Data

Register checkout_data processing via woocommerce_store_api_checkout_update_order_from_request:

• Receives the order and the full checkout request
• Save custom data to order meta

Declaring Block Compatibility

add_action( 'before_woocommerce_init', function() {
    if ( class_exists( \Automattic\WooCommerce\Utilities\FeaturesUtil::class ) ) {
        \Automattic\WooCommerce\Utilities\FeaturesUtil::declare_compatibility(
            'cart_checkout_blocks', __FILE__, true
        );
    }
});

Best Practices

• Declare cart_checkout_blocks compatibility in every extension
• Use the Store API (not REST API v3) for frontend/cart/checkout interactions
• Use @woocommerce/blocks-checkout hooks rather than DOM manipulation
• Enqueue block scripts only when the block is present on the page
• Follow Gutenberg coding standards for block development
• Test with both classic and block-based checkout
• Use block.json for block metadata (WordPress standard)

Fetch the WooCommerce Blocks extension docs and Block Editor handbook for exact API methods, slot names, and filter signatures before implementing.