The content of the internet is increasingly available on mobile devices. This naturally includes geodata in the form of maps, the display of which on small screens, optimization of data volumes to be transmitted, etc., represent a technical challenge. One of the most popular map viewers is currently OpenLayers, and its functionality on mobile devices will be the focus of the week-long Codesprint in Lausanne. The Codesprint is organized by swisstopo and camptocamp, and terrestris is supporting it by sending its chief developer Marc Jansen, who co-authored the book “OpenLayers – Web Development with Dynamic Maps and Geodata”, among other things.