Microsoft Excel 3.0 Worksheet (xls) 3
Readablespreadsheet · also known as Microsoft Excel Worksheet (3.0)
The Binary Interchange File Format (BIFF) is a spreadsheet file format developed by Microsoft. BIFF 3 is the native file format of Microsoft Excel 3.0 for Windows. The format is proprietary and Microsoft does not make details of its structure public. The information contained here is derived primarily from OpenOffice.org's reverse-engineered documentation of the format, and should not therefore be regarded as definitive. BIFF is a stream based format, and a BIFF 3 file comprises a single worksheet stream, containing a Beginning of File (BOF) record, followed by a series of Worksheet records, and terminated by an End of File (EOF) record.
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| Extensions | .xls |
|---|---|
| MIME types | application/vnd.ms-excel |
| Signatures | 09020600 at byte 0 (BIFF 3 Worksheet) |
| PRONOM | fmt/56 |
| Wikidata | Q60806040 |
| Apple UTI | com.microsoft.excel.xls |
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From PRONOM, Wikidata. Updated 2026-10-20.