Microsoft Excel 2000-2003 Workbook (xls) 8X

Readable

spreadsheet · also known as Microsoft Excel Workbook (XP-2003), Microsoft Excel Workbook (2002-2003)

The Binary Interchange File Format (BIFF) is a spreadsheet file format developed by Microsoft. BIFF 8X is a native file format of Microsoft Excel XP. The format is proprietary and Microsoft does not make details of its structure public. The information here is derived primarily from OpenOffice.org's reverse-engineered documentation of the format and should not therefore be regarded as definitive. BIFF 8X is based on Microsoft’s generic OLE2 Compound Document Format. An Excel workbook is stored as a ‘Book’ stream within a Compound Document Format file. The Book stream comprises a Workbook Globals Substream, containing a Beginning of File (BOF) record, the Workbook global records, and terminated by an End of File (EOF) record. This is followed by one or more Worksheet substreams, containing a Beginning of File (BOF) record, the worksheet records, and terminated by an End of File (EOF) record. The format remained unchanged with the release of Excel 2003.

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Extensions.xls.xlw
PRONOMfmt/62
WikidataQ60886323
Apple UTIcom.microsoft.excel.xls

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ToWithFidelityCommand and losses
Microsoft Excel for Windows 2007 onwardsLibreOfficePartialsoffice --headless --convert-to xlsx in.xls
Layout may shift; macros and some features are not kept.
OpenDocument Spreadsheet file format familyLibreOfficePartialsoffice --headless --convert-to ods in.xls
Layout may shift; macros and some features are not kept.
PDFLibreOfficePartialsoffice --headless --convert-to pdf in.xls
Fixed layout: the document is no longer editable.
Comma Separated ValuesLibreOfficeLossysoffice --headless --convert-to csv in.xls
First sheet only, values only: formulas, formatting and other sheets are lost.
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Sources

From Converters (FFmpeg, ImageMagick, Pandoc, LibreOffice), PRONOM, Wikidata. Updated 2026-10-20.

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