Although research on the use of (printed) mathematics textbooks and digital tools exists, there is still a high need for research on digital mathematics textbooks with integrated digital tools that are used by teachers and students in mathematics lessons.<br> Since 2019, the project KomNetMath researches the impact of a regularly used digital mathematics textbook at German secondary schools. The actual use, the impact on students’ beliefs towards the use of digital mathematics textbooks as well as the influence on mathematical competencies are of special interest.