Package Extension Catalog
These are the various file extensions to package files sorted by game.
All Unreal Packages share the same internal Package File Format, but:
- the format might be slightly different in different builds or in different games
- .[uc file]?, .ogg, .mp3, and various video files (.avi, .etc) are not Unreal packages
This means that technically most things can go into any package. For example textures can go in a .uax sound package, or static meshes be put into a .ut2 map package instead of a .usx static mesh package. This is how you can use the "MyLevel" pseudopackage to include custom content in a map, without having to make separate resource files.
Typical contents are just that, typical. .U packages especially, tend to have things besides UnrealScript binaries and sources in them.
All Unreal Engine Games
These extensions should work with any Unreal engine game.
| Extension | Description | Typical Contents |
| uc | UnrealScript Class Source | UnrealScript in plain ASCII Text. (This is not an Unreal package format. Here for reference only.) |
| u | UnrealScript Package File | Compiled UnrealScript and UnrealScript source text (without default properties). Often also contains Sounds, Textures, Meshes and Static Meshes |
| utx | Textures | Textures, sometimes compressed, and mipmaps |
| uax | Audio (sound) files | Wave sound files |
| uz / uz2 | Compressed package | Contains a compressed version(s) of any package for faster downloads. |
| uxx | Cached package | Cached downloaded package. The actual file extension is stored in Cache.ini in the game's Cache directory. This can be any of the other types of packages mentioned on this page. |
First generation
These extensions are used in Unreal1, Return to NaPali, and Unreal Tournament in addition to the universal extensions.
| Extension | Description | Typical Contents |
| unr | Unreal Map File | Map geometry and texture references as well as instances of any actors placed in map. Can also contain compiled UnrealScript code, sounds, textures, music, etc. |
| umx | Unreal Music Files | Contains a module music file. (usually S3M, IT or XM) |
Unreal Tournament 2003
These extensions are used in UT2003 in addition to the universal extensions.
| Extension | Description | Typical Contents |
| ut2 | UT2003 Map File | Map geometry and texture references as well as instances of any actors placed in map. Can also contain compiled UnrealScript code, sounds, textures, etc. |
| usx | Static Meshes | Contain geometry and texture references for static meshes. |
| ukx | Skeletal Meshes | Contains skeletal meshes. |
| uvx | Saved Ladder Profile | Contains information about the player's progress in UT2003's single player mode. |
| ogg | Ogg Vorbis Music File | (This is not an Unreal package format. Here for reference only.) |
Unreal 2: The Awakening
These extensions are used in U2 in addition to the universal extensions.
| Extension | Description | Typical Contents |
| con | DirectMusic CONtainer object | Music in Microsoft's proprietary "module" format that DirectX can read and use for playback |
| dlg | Unreal 2 Dialog file | Dialogs... something? |
| ogg | Ogg Vorbis Music File | (This is not an Unreal package format. Here for reference only.) |
| u2s | Unreal 2 Script File | Pawn scripting file, see AI Scripting for info |
| uax | Sound Package | Contain sounds. |
| ugx | ? | ? |
| un2 | Unreal 2 Map File | Map geometry and texture references as well as instances of any actors placed in map. |
| usx | Static Meshes | Contain geometry and texture references for static meshes. |
Deus Ex
These extensions are used in [Deus Ex]? in addition to the universal extensions.
| Extension | Description | Typical Contents |
| dx | Deus Ex Map File | Map geometry and texture references as well as instances of any actors placed in map. |
Wheel of Time
These extensions are used in the Wheel of Time in addition to the universal extensions.
| Extension | Description | Typical Contents |
| wot (?) | Wheel of Time Map File | Map geometry and texture references as well as instances of any actors placed in map. |
Rune, Rune: Halls of Valhalla
These extensions are used in Rune and Rune: Halls of Valhalla in addition to the universal extensions.
| Extension | Description | Typical Contents |
| run (?) | Rune Map File | Map geometry and texture references as well as instances of any actors placed in map. |
Undying
These extensions are used in Undying in addition to the universal extensions.
| Extension | Description | Typical Contents |
| sac | Undying Map File | Map geometry and texture references as well as instances of any actors placed in map. |
Star Trek DS9: The Fallen
These extensions are used in Star Trek DS9: The Fallen in addition to the universal extensions.
| Extension | Description | Typical Contents |
| dsm | DS9: The Fallen Map File | Map geometry and texture references as well as instances of any actors placed in map. |
Mobile Forces
These extensions are used in Mobile Forces in addition to the universal extensions.
| Extension | Description | Typical Contents |
| ??? | Mobiles Forces Map File | Map geometry and texture references as well as instances of any actors placed in map. |
America's Army: Operations
These extensions are used in America's Army: Operations in addition to the universal extensions.
| Extension | Description | Typical Contents |
| aao | Army Ops Map File | Map geometry and texture references as well as instances of any actors placed in map. |
| usx | Static Meshes | Contain geometry and texture references for static meshes. |
Related Topics
Githianki: I don't have the references with me since I am not at my gaming rig, so feel free to fill these in. I can't conclusively recall some of the map extensions right now. I know there are more games, like the Star Trek stuff but I don't have those or even know the full names. The format should be self-explanitory by looking at the edit box. I left some reference markup in the first table. It is all shamelessly ripped from the markup page anyway. I left out Unreal Championship and the PS2 titles since they can't be edited and who knows if the same file system was used in some cases anyway? Category To Do So this shows up if someone else wants to help out. It will take me awhile to get all info for the games I have (Unreal,NaPali,Ut,UT2003,Wot,RUNE,RUNE:HOV) I could get Army Ops too but I had to delete it to have room for UT2003 
Tarquin: There's probably some refactoring could be done between Engine Directory Structure, Package and here. Package is currently a redirect to Package, might be better to have a package overview page there.
Wormbo: Done some cleanup with the Wiki Markup on this page. It's cool stuff, but try not to overuse it.
Legal: Added Deus Ex, one of the best games EVER!
Githianki: Yeah I really got into the markup but it seemed useful here. I see how you cleaned it up so now I know the minimum needed. The markup page has lots of extra code which is where I lifted from. Maybe someone should clear that up or you'll be doing overtime. Fixed some typos. Added in .uz and .uxx extensions to universal. Can't believe I forgot Deus Ex. doh! Also, what was the scoop on .umx support in Ut2003 versions of the engine? Is it out or does the new opensource stuff support it? Also I think .uc can be RTF too. If so that should go back up there.
