Remove cf_id= in Caldera Forms

functions.php

<?php
// add this to your theme or child theme's functions.php file to 
// remove the cf_id=x from redirect URLs on form submit
function cf_remove_cfid( $url ){
    if( false !== strpos( $url, '?' ) ){
        $parts = explode( '?', $url );
        parse_str( $parts[1], $query );
        if( isset( $query['cf_id'] ) ){
            unset( $query['cf_id'] );
            return $parts[0] . '?' . http_build_query( $query );
        }
    }
    return $url;
}
add_filter( 'caldera_forms_redirect_url', 'cf_remove_cfid', 100 );