A fast, read-only radar for outdated Docker images. Cup reads the images behind your running Docker or Podman containers, asks each registry whether a newer digest or tag exists, and flags every result as a major, minor, or patch bump, a plain digest change, or up to date. Docker Hub, ghcr.io, Quay, lscr.io, and Gitea-style registries are supported, private ones through token authentication, and checks are designed not to exhaust registry rate limits. The browser dashboard on port 8000 counts monitored, outdated, up-to-date, and unknown images, adds search and filters, and opens any image to show its update type, check time, and a copyable pull command. Prefer automation? Schedule refreshes with a cron expression, trigger one through the API, or run the cup check command from a cronjob for table or JSON output. Rules in cup.json exclude images, ignore registries, and skip chosen update types, even per image. The JSON API feeds Homepage widgets, Home Assistant, and custom dashboards, one dashboard can aggregate several Cup servers, and agent mode serves the API without the interface. Cup only reports, so deciding when to update stays with you. Running on a dedicated VPS on RepoCloud with guaranteed CPU, RAM, and SSD, full root SSH access, and a browser serial console. AGPL-3.0 licensed.