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Understanding Excel binary workbook package

XLSB is Excel's binary workbook since Excel 2007, a ZIP package with binary parts instead of XML. See how it differs from XLSX and XLS.

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An XLSB file is Excel's binary workbook, an option since Excel 2007. It uses the same ZIP package as XLSX, but the sheets and other parts are binary records rather than XML, rather than XML. Microsoft specifies it as MS-XLSB; it is not an international standard. An XLSB can hold formulas and macros; check that your chosen program supports it. Klarbon support is planned, not available yet.

What is in an XLSB package?

Part Holds
[Content_Types].xml and relationships the package structure, as in XLSX
.bin parts the workbook, the sheets, their data and formulas, in binary records
Supporting parts metadata such as core.xml, in XML
Property Value
Container ZIP, Open Packaging Conventions
Content binary records
Specification Microsoft MS-XLSB
Macros allowed
International standard no

Microsoft publishes MS-XLSB, and the Library of Congress describes the package, the macro support and the conversion to XLSX (MS-XLSB, Library of Congress).

XLSB, XLSX or XLS?

XLSB XLSX XLS
Container ZIP ZIP compound file
Content binary records XML binary records
Macros yes no, XLSM instead yes
Decoder needed XLSB-specific OOXML spreadsheet BIFF compound file

What does Klarbon do with XLSB files?

Klarbon does not open XLSB files today; reading bank transactions from an XLSB sheet, with a column mapping you confirm, is planned, not available yet. Klarbon does not run macros or calculate formulas from a file. Klarbon writes bank statements as XLSX; see supported bank statement files.

Frequently asked questions

What is an XLSB file?

An Excel binary workbook, an option since Excel 2007. It uses the same ZIP package as XLSX, but the sheets and other parts are stored as binary records instead of XML. Opening speed depends on the workbook and software.

Is XLSB the same as XLSX?

No. The package looks alike, but the parts inside are binary, so a program that reads XLSX cannot read XLSB without its own decoder. Check that your chosen program supports XLSB.

Can an XLSB file contain macros?

Yes. Unlike XLSX, where a workbook with macros must be saved as XLSM, an XLSB can hold macros. Do not enable them in a file from an unknown sender.

Can XLSB be converted to XLSX without loss?

Check the workbook after conversion. XLSX cannot store VBA macro code; use a macro-enabled format such as XLSM if macros must be preserved.

Sources

Updated 5 November 2026

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