A Celtx developer works on the Celtx software, a pre-production tool for creating scripts, storyboards, and production schedules. Their responsibilities include developing new features, fixing bugs, and improving the software's performance and usability. They work closely with other developers, designers, and product managers to understand user needs and translate them into software solutions. Additionally, they ensure the software is compatible across various operating systems and devices. They may also help write technical documentation and support materials. Their goal is to create a powerful, intuitive tool that helps filmmakers and writers streamline their pre-production process.