The ‘AR Number Line’ app is an innovative augmented reality application for mathematics education and the development of mathematical skills. The app links real-world proportions with a virtual “endless” number line. By placing the interactive number line in real space and allowing users to move along it, mark numbers, or transitions between numbers, the app enables a new way to explore numbers and numerical relationships. Special potential is evident in larger number ranges, which are typically only visualized in segments or greatly reduced in size. The app is a pre-release version in development, but it is already functional and is currently undergoing a scientific trial phase in elementary schools. The app will continue to be actively developed during the evaluation phase, and insights will be incorporated into future updates.