File extension
.mdb
Microsoft Access Database (MDB) format
.mdb files are Microsoft Access databases: single-file relational databases built on the Jet/ACE engine that hold tables, queries, forms, reports, and application logic together in one file.
Known meanings
Formats and reference material for .mdb
Microsoft Access Database (MDB) format
Single-file Jet/ACE relational database used by Microsoft Access
Details
Format notes
Microsoft Access Database (MDB)
An .mdb file is a self-contained Microsoft Access database. Unlike a
client/server database, the whole database — table definitions, row data,
indexes, relationships, queries, and often the application user interface —
lives inside a single file backed by the Jet database engine. This made MDB a
popular format for departmental applications, desktop data tools, and data
handed between users as a single attachment.
Beyond raw tables, an .mdb can embed a complete application: parameterized
queries, forms, reports, macros, and VBA modules. That means the file often
carries both data and executable logic, which is important when assessing,
migrating, or archiving it.
Versions And The ACE Successor
MDB is the format used through Access 2003 and the Jet engine. Access 2007
introduced the .accdb format and the Access Connectivity Engine (ACE), which
added features such as multi-value and attachment fields and stronger
encryption, while dropping some legacy replication and user-level security
features. Both formats remain in use, and tools frequently need to distinguish
them because a .mdb and an .accdb are not byte-compatible.
The file format itself is proprietary and was reverse-engineered by the
community. Open-source projects such as MDB Tools allow reading table schemas
and exporting data from .mdb files on platforms without Access installed,
which is valuable for extraction and preservation workflows.
Preservation Notes
Because an MDB can contain queries, forms, and VBA rather than just data, a faithful archive may need to record the Access version, linked external tables, and any application logic — not only the table contents. For long-term preservation, exporting tables to an open, documented format (such as CSV or SQL) alongside the original file preserves the data even where the Access runtime is unavailable.
Security Notes
MDB files can contain VBA macros and can link to external data sources, so an
untrusted .mdb should be treated as potentially active content, not inert
data. Historic Jet security relied on a shared workgroup file and weak
encryption that should not be considered protective today. Open unknown Access
databases with macros disabled and inspect embedded code before trusting it.
Further Reading
- Microsoft Access overview:
https://en.wikipedia.org/wiki/Microsoft_Access - MDB Tools project:
https://github.com/mdbtools/mdbtools