Wikis / Unreal Wiki / Legacy:File Format

The Unreal Engine uses many different file formats. On this page we present an overview of them all.

Package File

The Unreal Engine has one principal file format, the package. It's this that stores all the Unreal resources: maps, textures, compiled UnrealScript classes, etc.

There is only one Package File Format for all the extensions listed, so in fact any package can hold any type of resource, irrespective of where it is kept and its extension. But the usual contents are:

• U file – UnrealScript classes compiled with ucc
• UNR file / UT2 file - Map Files
• UTX file – textures and materials
• UMX file – music
• UAX file – sound
• UKX file – animations
• UZ file / UZ2 file – Unreal zip (can be compressed and decompressed with ucc)

Map files can have other resources embedded within them; see MyLevel or Embedding code.

Each type of package should be put in specific subfolder: see Engine Directory Structure. Despite being in different folders and having different extensions, the engine considers only the package name. This means that two packages such as:

/Sounds/Foo.uax
/Textures/Foo.utx

will be considered by the engine as the same package, which will cause considerable problems. The usual way to be sure you don't use the same name twice is to append the type of resource to the name, eg MyProjectSounds.uax, MyProjectTextures.utx.

Other formats

Installers:

• UMOD/UT2MOD – Unreal Module or UT2003 Module files are installer packages for the Unreal engine.

Mapping:

• T3D file – brush saved by UnrealEd
• 2DS file – 2D shape saved by the UnrealEd 2D Shape Editor

Coding:

• INI file – see Config Vars And .Ini Files
• INT file – see also localization
• UC file – UnrealScript source code
• UPL file – see UPL File
• UPKG file – Package flags

Importable:

• DXF file
• ASC file
• LWO file
• ASE file format
• OBJ file

Other importable formats:

• WAV file – wave files are imported and saved as .uax
• 3D file – LOD Mesh and Animation data used by early builds of UnrealEngine 1.0, see 3ds2unr
• PSK file – Skeletal Mesh file, see Skeletal_Mesh
• PSA file – Skeletal Animation file

Other file formats recognized by the engine:

• OGG file – for music and sound
• Ucs file – for AI scripting
• KA file – for Karma data (ragdolls?)

Related Topics

• Unreal Engine
• Engine Directory Structure
• Package Extension Catalog