The experiments at the Large Hadron Collider (LHC) at CERN have been running for more than a decade. The data recorded by the detectors such as the CMS experiment are analysed by thousands of physicists all over the world. The CMS Collaboration has made openly available more than 2.5 petabytes of data on the CERN Open Data Portal, containing billions of recorded and simulated events.

Open Data are, however, only useful when accompanied by realistic usage examples. The sheer amount of data as well as the fact that the software used to analyse them is often more than ten years old poses several challenges. In this presentation, Clemens will discuss how the CMS Data Preservation and Open Access group tries to overcome these challenges so that potentially everyone could use the data to unveil hidden physics.