Hack4Europe is holding four hackathons across Europe to encourage developers to build applications using the Europeana Search API and Linked Data Pilot. Winners will be selected in categories like commercial potential, social impact, and innovation. Developers can access technical documentation on the Europeana Labs website to build applications using over 19 million metadata records from Europeana, Europe's digital platform for cultural heritage. Organizers will be available during the hackathons to answer any questions.