.UZ2 files used by Unreal engine (e.g. UT2004) to exchange game resources (setup, server data).

UZ2 files has double extension much like GZ or BZ2 files - test.exe.uz2 for example.

Each file consists of one or more parts of deflated compressed streams. Each part has following structure:

uint32 compressed; // compressed size
uint32 size; // uncompressed size
// <compressed stream>