The MUI AmigaOS development team is proud to announce the immediate release of version 5.0-2017R1 of the Magic User Interface for AmigaOS4 and AmigaOS3. The new update comes with improvements and bugfixes. MUI is the abbreviation of Magic User Interface, an object-oriented BOOPSI-driven user interface framework for AmigaOS-based operating systems. It features a flexible user interface where end-users can define the Look&Feel of applications using MUI in high detail. Beside this end-user flexibility MUI comes with a wide variety of so-called Custom Classes which developers using MUI can use in their applications and which provide additional functionality (e.g. such as a full-fledged text editor). This third-party custom class functionality as well as the high user flexibility in defining the Look&Feel of a MUI applications makes MUI the most advanced user interface framework for AmigaOS computer systems today. Like all former releases a keyfile is required to enable all available settings. Old keyfiles from MUI 3.8 can be used without any restriction.