A Gephi developer utilizes the Gephi software, an open-source network analysis and visualization tool, to create complex interactive visualization, exploration, analysis, and manipulation of all types of networks and complex systems. They handle data input in various formats, analyze the network data, and utilize built-in algorithms to reveal patterns and trends. They work on designing and developing custom plugins for additional functionality. Gephi developers also interpret the visualization results to provide insights, and they collaborate with data analysts, scientists, or researchers. They are often involved in social network analysis, link analysis, and biological network analysis.