Flex framework library used by Adobe Flash Player to store a collection of digitally signed Runtime Shared Libraries (RSL files).

These .SWZ files contain common components used in many Flash applications, and because they are digitally signed by Adobe, once they are downloaded they are automattically stored in Flash Player's cache and can be used later by a different Flash application if required.

One of the advantages of this method is that once a .SWZ file has been download and cached by Flash Player, other Flash applications that require the same resouces do not need to download the library again, resulting in a reduction in the time it takes for the Flash application to load.