XLS (Microsoft Excel Binary Spreadsheet)

XLS is the legacy binary spreadsheet format used by Excel 97-2003. It stores worksheets, formulas, and charts in a proprietary compound binary structure. While superseded by XLSX, many legacy systems still generate and require .xls files.

MIME Type

application/vnd.ms-excel

Type

Binary

Compression

Lossless

Advantages

+ Broad compatibility with older Excel versions and legacy enterprise tools
+ Well-documented binary format with mature parsing libraries
+ Supports VBA macros and embedded objects

Disadvantages

− Row limit of 65,536 and column limit of 256 per worksheet
− Larger file sizes than compressed XLSX
− Proprietary binary format is harder to work with programmatically

When to Use .XLS

Use XLS only when interfacing with legacy systems that cannot read XLSX; for all other cases prefer XLSX or CSV.

Technical Details

XLS uses the BIFF8 record format within an OLE2 compound document. Each record type encodes cell values, formulas, formatting, and sheet metadata in a sequential binary stream.

History

The binary .xls format was the dominant spreadsheet format throughout the late 1990s and 2000s. Microsoft BIFF8 (Binary Interchange File Format) was the last major binary revision before the shift to Open XML.

Convert from .XLS

.xls → .csv .xls → .ods .xls → .tsv .xls → .xlsx

Convert to .XLS

.csv → .xls .ods → .xls .tsv → .xls .xlsx → .xls

Related Formats

.doc .docx .epub .html .keynote .md .mobi .numbers .odp .ods

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