Free online MDB to ACCDB converter

A newer Microsoft Access installation may require ACCDB to use features such as attachments or multivalued fields. Converting an older database also creates a current-format copy for editing, while preserving the original MDB for older applications.

What the MDB format is

MDB is the Microsoft Access database format used by Access 2003 and earlier, although several earlier Access releases also created MDB files. A single MDB file can contain tables, queries, forms, reports, macros, VBA modules, relationships, indexes, and database settings.

MDB files remain common in legacy business applications, inventory systems, departmental databases, and archived Access projects. Access 2007 and later can generally open compatible MDB files, but Access 2003 and earlier cannot open ACCDB files.

What the ACCDB format is

ACCDB is the default Access database format introduced with Access 2007. It supports newer data types and features, including attachment fields, multivalued fields, and calculated fields. It is the appropriate format for databases that will be maintained in Access 2007 or later.

ACCDB is not backward-compatible with Access 2003 or earlier. It also removes or changes support for some legacy features, so keeping the original MDB until testing is complete is necessary.

How to convert the database in Microsoft Access

1. Make a backup copy of the original .mdb file and work on the copy.
2. Open the copy in Microsoft Access 2007 or a later desktop version.
3. Choose File → Open → Browse, select the MDB file, and provide its database password if requested.
4. Choose File → Save As, then select Access Database (*.accdb). In some Access versions the command appears under File → Save As → Save Database As.
5. Enter a new filename and location, then select Save. Access creates an ACCDB copy and leaves the MDB unchanged.
6. Open the ACCDB and test representative tables, queries, forms, reports, macros, linked tables, and VBA procedures before distributing or replacing the MDB.

If Access reports database errors, run Database Tools → Compact and Repair Database on a backup copy, then repeat the conversion. Very old MDB variants may not open directly in the installed Access version; use the Access release that created the file or an appropriate intermediate release before saving it as ACCDB.

Converting without desktop Access

You can convert an MDB file for free on 101convert.com without installing software. Upload the file, choose ACCDB as the output format, start the conversion, and download the generated file when processing finishes. Do not upload confidential, personal, financial, or regulated data unless the service satisfies your organization’s security and retention requirements.

Compatibility and conversion limitations

• Legacy security: ACCDB does not support the MDB workgroup-based user-level security model. Permissions from an MDB secured with an MDW workgroup file should not be assumed to carry over; use Windows permissions, Access encryption, or another access-control design as appropriate.
• Replication: ACCDB does not support the replication features available in some MDB databases. Replicated databases need an alternative synchronization design.
• Linked data: Saving the Access front end as ACCDB does not convert data in linked MDB files, ODBC databases, spreadsheets, or other external sources. Verify each connection and update drivers or connection strings if necessary.
• VBA and controls: Modules and VBA code may be retained, but missing references, obsolete ActiveX controls, outdated API declarations, and unavailable add-ins can break forms, reports, or automation.
• Passwords and encryption: A protected MDB must be opened with valid credentials. Test access after conversion and apply current encryption and operating-system permissions when protecting sensitive data.
• File size: Converting to ACCDB does not remove the Access database size limit; MDB and ACCDB databases are generally limited to 2 GB, excluding linked data.
• Backward compatibility: Keep an MDB copy or export if any required computer, application, or user still depends on Access 2003 or an earlier release.