Weasis is a multipurpose web-based viewer with a highly modular architecture. It can connect to any PACS server supporting WADO via a web portal. In particular, it has been used with the DCM4CHEE PACS server. Weasis provides a wide range of image viewing tools in an application that may automatically be downloaded along with a data set accessed from a web server. It can also be run as a platform independent Java stand-alone application and stored on a DVD along with a data set. It uses a plugin architecture to allow expansion through software components.