Unreal Engine 4 PAK

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PAK

• Format Type : Archive
  
• Endian Order : Little Endian
  
• Signature : E1 12 6F 5A
  

Format Specifications

// Unreal Engine 4 PAK file format
FILE DATA
  for each file
    uint64 {8}       - null
    uint64 {8}       - Compressed Length (not including the file header fields or padding)
    uint64 {8}       - Decompressed Length
    uint32 {4}       - Compression Type (0=uncompressed, 1=ZLib, 2=GZip, 4=Snappy, 16=bias memory, 32=bias speed)
    byte {20}        - data sha1 hash
    if (compressed){
      uint32 {4}       - Number of Compressed Blocks
      for each compressed block
        uint64 {8}       - Offset to the start of the compressed data block (relative to the start of the archive)
        uint64 {8}       - Offset to the end of the compressed data block (relative to the start of the archive)

      byte {1}         - null
      for each compressed block
        uint32 {4}       - Decompressed Length of thie block
        byte {X}         - File Data (ZLib Compression)

      byte {0-2047}    - null Padding to a multiple of 2048 bytes (sometimes, not always)
      }

    else if (uncompressed){
      uint32 {4}       - null
      byte {1}         - null
      byte {X}         - File Data
      byte {0-2047}    - null Padding to a multiple of 2048 bytes (sometimes, not always)
      }

DIRECTORY
  uint32 {4}       - Relative Directory Name Length (including null terminator) (10)
  byte {9}         - Relative Directory Name (../../../)
  byte {1}         - null Relative Directory Name Terminator
  uint32 {4}       - Number of Files
  for each file
    uint32 {4}       - Filename Length (including null terminator)
    byte {X}         - Filename
    byte {1}         - null Filename Terminator
    uint64 {8}       - File Offset
    uint64 {8}       - Compressed Length (not including the file header fields or padding)
    uint64 {8}       - Decompressed Length
    uint32 {4}       - Compression Type (0=uncompressed, 1=ZLib, 2=GZip, 4=Snappy)
    byte {20}        - Unknown
    if (compressed){
      uint32 {4}       - Number of Compressed Blocks
      for each compressed block
        uint64 {8}       - Offset to the start of the compressed data block (relative to the start of the archive)
        uint64 {8}       - Offset to the end of the compressed data block (relative to the start of the archive)

      byte {1}         - null
      uint32 {4}       - Decompressed Block Size (65536 if multiple blocks, otherwise the same as the decompressed length)
      }

    else if (uncompressed){
      uint32 {4}       - null
      byte {1}         - null
      }

FOOTER (44 bytes)
  uint32 {4}       - Signature ((bytes)225,18,111,90) // E1 12 6F 5A // "..oZ"
  uint32 {4}       - Version // 1, 2, 3, 4, 7, 8, 9 or 11
  uint64 {8}       - Directory Offset
  uint64 {8}       - Directory Length (not including FOOTER)
  byte {20}        - directory sha1 hash
  if (version) == 11
    char {160} - compression string + padding // e.g. "Zlib"

Notes and Comments

• It is popular file format used in many games made on Unreal Engine 4.
• These files normally occur in path such as "\<game_name>\<build_name>\Content\Paks\<build_name>-WindowsNoEditor.pak"
• This archive type uses ZLIB, GZIP or Snappy compression method.
• Data may be encrypted with AES encryption.
• To parse the archive, footer needs to be read first, because it has important info about offsets.

Games

List of games using this file format:

• Backbone (PC) (*.PAK) (version 11)
• Little Nightmares II (PC) (*.PAK) (version 8)
• Poppy Playtime (PC) (*.PAK) (version 11)
• Pumpkin Jack (PC) (*.PAK) (version 9)
• Styx: Shards of Darkness
• Tekken 7 (PC) (*.PAK) (version 3)
• The Fall of Lazarus
• Many more...

QuickBMS Scripts

See List of Unreal Engine Tools article on this wiki.

Compatible Programs

See List of Unreal Engine Tools article on this wiki.

See Also

• UE4 keys collection
• Unreal Engine 4 UASSET (xentax wiki)

Gallery

• 

  FModel

• 

  UE4 PAK Unpacker