Transparent thin-film heaters have sparked great interest in both the scientific and industrial sectors due to their critical role in various technologies, including smart windows, displays, actuators, and sensors. In this review, we summarize the structural design, fabrication methods, properties, and materials used in thin-film heaters. We also discuss methods to improve their efficiency and recent advancements in the field, and provide insights into the market size, growth, and future outlook for thin-film heaters.