Berger-Levrault is an international company that developed applications in GWT for more than 10 years. However, GWT is no longer actively maintained, with only one major update since 2015. To avoid being stuck with legacy technology, the company decided to migrate its applications to Angular. However, because of the size of the applications (more than 500 web pages per application), rewriting from scratch is not desirable. To ease the migration, we designed a semi-automated migration approach that helps developers migrate applications' front-end from GWT to Angular and a tool that performs the migration. In this paper, we present our approach and tool. We validated the approach on concrete application migration and compared its benefits to redeveloping the application manually. We report that the semi-automated migration offers an effort reduction over a manual migration. Finally, we present recommendations for future migration projects.