Arm-based processors are starting to reach performance levels and provide features that make them highly attractive for supercomputing. This Hackathon will provide application developers with the opportunity to learn about porting scientific computing applications to and how to optimise them for Arm-based architectures. Participants ideally come with their own codes or codes they are working with. During (and after) the Hackathon access to two different types of Arm-based servers at Jülich Supercomputing Centre (JSC) will be provided. Experts from Arm will be available for training lectures and hands-on sessions.