Entri is a company that provides an API for custom domains, designed to simplify the process of integrating with DNS providers and obtaining SSL certificates. Their platform allows developers to add support for custom domains with minimal coding, offering a quick and efficient solution for enhancing user experience and generating new revenue streams. Entri specializes in facilitating easy DNS integrations and hassle-free SSL management, making it an attractive option for both startups and enterprises looking to streamline their domain management processes.