What is the WAB file format?
A .wab file is a Windows Address Book - a binary contact database used by Outlook Express and older Windows Mail to store personal contact information. Introduced in 1996 alongside Internet Explorer 3, the WAB format served as the shared address book for Microsoft's email clients through the Windows XP era.
Each .wab file is managed exclusively through the wab32.dll API; the file cannot be opened directly on a modern system because that library was removed in Windows 7. The binary store uses a MAPI-style property format - each contact record is a collection of typed properties (display name, email address, phone numbers, postal address, group membership) indexed by MAPI-like property IDs.
On Windows XP, the default address book was stored at %APPDATA%\Microsoft\Address Book\<username>.wab. The format went through several revisions across Internet Explorer 3 through 6 and Outlook Express 4 through 6, and files are not always interchangeable between major versions.
Windows Vista replaced the WAB format with Windows Contacts - XML-based .contact files. The wab.exe utility and wab32.dll were removed from Windows 7 and later. Opening a .wab file on a modern Windows system requires third-party conversion tools to extract contacts as .vcf (vCard) files or import them into Outlook.
Security & safety
RISK: LOWWAB files are passive contact databases with no executable content. Risk is primarily privacy-related: they contain personal data (names, e-mails, phone numbers) of potentially hundreds of contacts. Handle old WAB backups with appropriate care to avoid data leakage. Third-party WAB converters that require upload should be trusted sources; avoid uploading personal contacts to unknown web services.
Format details
in a nutshellPrograms that open WAB files
Windows2 apps
WAB Converter (convert.guru)
Free Upload the .wab file online; download contacts as CSV, VCF, or PST.
Windows Contacts (built-in, Vista only)
Built-in On Windows Vista: double-click to import via Windows Contacts built-in importer. Technical details
deep spec| API layer | Managed exclusively through `wab32.dll`; no documented public binary format - all access via the WAB COM API |
| Internal structure | MAPI-style property store; each contact stored as an array of typed property ID-value pairs (not OLE2/CFBF) |
| Encoding | Binary, little-endian |
| Default file path (Windows XP) | `%APPDATA%\Microsoft\Address Book\<username>.wab` |
| Stored property types | Display name, email address(es), phone numbers, postal address, notes, photo, and group membership |
| Version compatibility | Format revised across IE3 / OE4 / OE5 / OE6; files are not always interchangeable between major versions |
| OS availability | Windows 95 through Windows XP; `wab32.dll` and `wab.exe` removed from Windows 7 and later |
| Typical file size | 10 KB - 5 MB (scales with number of stored contacts and attached data) |
| Group support | Contact distribution lists stored within the same `.wab` file alongside individual contacts |
| Migration path | Export to `.vcf` (vCard) or `.csv` via third-party tools; Windows Vista's Windows Contacts imported `.wab` files natively |
| Released | 1996 (Internet Explorer 3 / Outlook Express 1) |
| Latest version | WAB 6.x (Windows XP era; component shipped with wab32.dll) |
| Specification | learn.microsoft.com |
WAB conversions
Community Q&A
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