ACCDB vs MDB: what’s the difference?
Both are Microsoft Access databases. The difference between ACCDB and MDB is mostly age: .mdb is the format Access used up to 2003, and .accdb is the one it has used since Access 2007. Here is what changed, and what it means when someone sends you one.
Short answer
.mdb is the older Access format, made by Access 97 to Access 2003. .accdb replaced it in Access 2007 and is the default today. ACCDB added attachment fields, multi-value fields and stronger password encryption; MDB kept a few things ACCDB dropped, such as user-level security. Both hold tables, queries and relationships, and both top out at 2 GB.
Get Keyfield Opens .accdb and .mdb files. Viewing is free, with no account.
The difference in one table
| .mdb | .accdb | |
|---|---|---|
| Made by | Access 97 to Access 2003 (and later versions, when asked to) | Access 2007 and every version since |
| Database engine | Jet | ACE, Jet’s successor |
| Attachment fields | No | Yes: several files per record, stored inside the database |
| Multi-value fields | No | Yes |
| Database password | A password Access checks when it opens the file | Encryption with the password; stronger from Access 2010 |
| User-level security, replication | Yes | No |
| Largest size | 2 GB | 2 GB |
Both formats hold the same core things: tables, saved queries, relationships, and in the desktop program, forms, reports, macros and code.
Why there are two
For its first decade and more, Access stored everything in .mdb files read by the Jet database engine. Access 2007 introduced a new engine and a new file format, .accdb, so it could add field types that the old format couldn’t hold. The attachment type stores whole files, a PDF or a photo, inside a record. Multi-value fields hold a short list of choices in one field. Access 2010 then made the encryption you get by setting a database password much stronger.
To make room for that, .accdb dropped two old features: user-level security, where a separate workgroup file decided who could open what, and replication. That is why some old business databases were never converted: they relied on one of the two.
Which one have you got?
- The extension tells you the format, but not the exact version. An
.mdbcan be from Access 97, 2000 or 2002–2003. Keyfield shows the version on the database screen, for example “Access 97” or “Access 2016”. .laccdband.ldbare not databases. They are lock files Access creates while someone has the database open. If that is all you were sent, ask for the.accdbor.mdbitself..accdeand.mdeare compiled copies with the design locked, made for handing out. Keyfield is built for.accdband.mdb.
Which one opens where
Current versions of Access open both, with one gap: Access 2013 and later no longer open Access 97 files, which have to go through an older Access first (how to open an Access 97 MDB file today). On a phone, neither format opens without an app made for it. Keyfield reads both, from Access 97 to Access 2019, read-only. Files from Access 2.0 (1994) are older than it reads, and .accdb files encrypted by Access 2010 or later don’t open yet.
For the step-by-step on a phone, see how to open an ACCDB file on Android. If yours refuses, here are the usual reasons.
Open either kind on your phone
Keyfield opens .mdb and .accdb files from Access 97 to 2019 and tells you which version you have. Viewing is free; nothing in the file is changed.
