This is a preprint of our tool paper accepted at MSR 2019. Abstract: Deploying software packages and services into containers is a popular software engineering practice that increases portability and reusability. Docker, the most popular containerization technology, helps DevOps practitioners in their daily activities. Despite being successfully and increasingly employed, containers may include buggy and vulnerable packages that put at risk the environments in which the containers have been deployed. Existing quality and security monitoring tools provide only limited support to analyze Docker containers, thus forcing practitioners to perform additional manual work or develop ad-hoc scripts when the analysis goes beyond security purposes. This limitation also affects researchers desiring to empirically study the evolution dynamics of Docker containers and their contained packages. To overcome this limitation, we present ConPan, an automated tool to inspect the characteristics of packages in Docker containers, such as their outdatedness and other possible flaws (e.g., bugs and security vulnerabilities). ConPan comes with a CLI and API, and the analysis results can be presented to the user in a variety of formats.