OpenTuner is an extensible framework designed for program optimization across a diverse range of applications. It provides a customizable search technique that allows users to tailor the optimization process to specific needs, making it suitable for a variety of domains and types of software. OpenTuner integrates multiple search strategies, which can be adapted and extended to improve the performance of programs by automatically exploring various tuning configurations. It is especially useful for researchers and developers seeking to experiment with and refine performance tuning parameters.