Remove /category/ from category (archive) page URLs (without using a plugin)

Please add this code in functions.php to remove the “category” text from permalink.

function remove_category( $string, $type ) {
    if ( $type != 'single' && $type == 'category' && ( strpos( $string, 'category' ) !== false ) ){
        $url_without_category = str_replace( "/category/", "/", $string );
        return trailingslashit( $url_without_category );
    }
    return $string;
}
add_filter( 'user_trailingslashit', 'remove_category', 100, 2);