Admidio is membership management software for clubs, associations, and groups, built so that every permission follows from the roles a person holds. Organizers define roles such as board, youth team, or trainers, decide who may email or see each one, and grant module rights like managing events, editing contacts, or uploading photos with simple switches. Contact records use customizable profile fields, record relationships such as parent and child, and can be imported in bulk or exported as vCards. New members register online and administrators review each request. Events carry dates, venues, calendars, and participant lists with sign-up, and the schedule downloads as iCal. Messages go as HTML email to individuals, roles, or groups, and members also find announcements, a categorized forum, document folders with role-based access, and photo albums with e-cards. The inventory manager tracks equipment, who holds it, and its borrowing history. Optional two-factor login protects accounts, a change history can be switched on for every module, and single sign-on lets other applications authenticate against the member database. Twenty-five languages are included, the interface installs as a progressive web app, and sub-organizations can be managed from the same installation. Running on a dedicated VPS on RepoCloud with guaranteed CPU, RAM, and SSD, full root SSH access, and a browser serial console. GPL-2.0 licensed.