A Chargify developer primarily works on the Chargify platform, a billing and subscription management tool. They design, develop, implement, and maintain software applications that integrate with the Chargify API. Their tasks may include creating custom features, troubleshooting technical issues, and optimizing system performance. They also collaborate closely with other team members to ensure the platform meets business needs and user requirements. Furthermore, they may be involved in testing and quality assurance of the platform, ensuring its reliability and efficiency. They must have a deep understanding of web technologies and payment gateways to ensure secure and seamless transactions.