First Page

The first page of a database contains various properties.

The first 24 bytes of the header identify the file format:

Name Offset Length Type Description
Magic Number 0x00 4 bytes UINT 32 LE 0x100
File format ID 0x04 16 bytes CHAR A zero-terminated string identifying the file format
  • MDB format (Access 97-2003): "Standard Jet DB"
  • ACCDB format (Access 2007-2010): "Standard ACE DB"
Jet Version 0x14 4 bytes UINT 32 LE JET file format version
  • 0 Access 97 (Jet 3)
  • 1 Access 2000, 2002/2003 (Jet 4)
  • 2 Access 2007
  • 0x103 Access 2010

The next 126 (Jet 3) / 128 or so (Jet 4) bytes are encrypted with the RC4 key 0x6b39dac7:

0x00 34 bytes
System Collation (Jet 3) 0x22 2 bytes UINT 16 LE Jet 3 only, default collation.
System Code Page 0x24 2 bytes UINT 16 LE The system code page used in this database. Used for field names etc in Jet 3, used for OLE fields in Jet 4.
Database Key 0x26 4 bytes UINT 32 LE If this is 0, the database is not encoded.
Database password 0x2A 20 bytes (Jet 3)
40 bytes (Jet 4)
Obfuscated in Jet 4
24 bytes (Jet 3)
4 bytes (Jet 4)
System Collation (Jet 4) 0x56 2 bytes UINT 16 LE Jet 4 only, default collation. Unknown what this contains in Jet 3.
Creation date 0x5A 8 bytes DOUBLE The creation date of the database, stored in Microsofts strange date format (days since 1900 or so). Used for obfuscating the password in Jet 4.
28 bytes (Jet 3)
32 bytes (Jet 4)