Add custom HTML to the WooCommerce order confirmation email and thank you page

functions.php

// Add custom HTML to the WooCommerce thank you page
add_action('woocommerce_thankyou', 'custom_html_confirmation_page_1001');
function custom_html_confirmation_page_1001($order_id) {
    $order = wc_get_order($order_id);
    echo '<div class="custom-confirmation-message">';
    echo '<h2>Thank you for your purchase!</h2>';
    echo '<p>Your order number is: ' . $order->get_order_number() . '</p>';
    echo '<p>We appreciate your business and will send you a confirmation email shortly.</p>';
    echo '</div>';
}

// Add custom HTML to the WooCommerce order confirmation email
add_action('woocommerce_email_order_details', 'custom_html_confirmation_email_1001', 10, 4);
function custom_html_confirmation_email_1001($order, $sent_to_admin, $plain_text, $email) {
    if (!$sent_to_admin && $email->id === 'customer_processing_order') {
        echo '<div class="custom-email-message">';
        echo '<h2>Thank you for shopping with us!</h2>';
        echo '<p>Your order number is: ' . $order->get_order_number() . '</p>';
        echo '<p>We are preparing your order for shipment and will update you with tracking details soon.</p>';
        echo '</div>';
    }
}