Add a newsletter subscription checkbox form on WooCommrece Register Page

Question

I'm using SendGrid plugin which allows to create a Newsletter Subscription Form that will send email notification to subscribe to newsletter (https://sendgrid.com/docs/for-developers/sending-email/wordpress-subscription-widget/).

I want that when a new user sign-up they will have an option to subscribe on newsletter through checkbox on Register Page (http://prntscr.com/nmq8h2).

Answer 1

The SendGrid plugin is not anymore maintained since a while (so it seems really outdated).

Updated: Now to add a checkbox for a news letter subscription in Woocommerce registration form (and on My account > Account details section), you will use the following:

// Remove "(optional)" label for this checkbox
add_filter( 'woocommerce_form_field' , 'remove_optional_custom_field_label', 10, 4 );
function remove_optional_custom_field_label( $field, $key, $args, $value ) {
    if( 'receive_newsletter' === $key && is_wc_endpoint_url( 'edit-account' ) ) {
        $optional = '&nbsp;<span class="optional">(' . esc_html__( 'optional', 'woocommerce' ) . ')</span>';
        $field = str_replace( $optional, '', $field );
    }
    return $field;
}

// Display a custom checkbox in My Account > Account details
add_action( 'woocommerce_register_form', 'add_account_newsletter_checkbox_field' );
add_action( 'woocommerce_edit_account_form', 'add_account_newsletter_checkbox_field' );
function add_account_newsletter_checkbox_field() {
    woocommerce_form_field( 'receive_newsletter', array(
        'type'  => 'checkbox',
        'class' => array('form-row-wide'),
        'label' => __( 'Subscribe to our newsletter?', 'woocommerce' ),
        'clear' => true,
    ), get_user_meta(get_current_user_id(), 'receive_newsletter', true ) );

}


// Save registration checkbox field value
add_action( 'woocommerce_created_customer', 'save_account_registration_field' );
function save_account_registration_field( $customer_id ) {
    $value = isset( $_POST['receive_newsletter'] ) ? '1' : '0';
    update_user_meta( $customer_id, 'receive_newsletter', $value );

}

// Save checkbox field value for My Account > Account details
add_action( 'woocommerce_save_account_details', 'save_account_details_newsletter_checkbox_field', 10, 1 );
function save_account_details_newsletter_checkbox_field( $user_id ) {
    $value = isset( $_POST['receive_newsletter'] ) ? '1' : '0';
    update_user_meta( $user_id, 'receive_newsletter', $value );
}

Code goes in functions.php file of your active child theme (or active theme). Tested and works.

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1) On WooCommerce Registration form:

2) On My account > Account details (section):

Now as this your plugin is outdated and as the rule on StackOverFlow is one question at the time, you will have to handle the Sendgrid Newsletter integration (as it's anyway something too broad).