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Some of our original research is documented at

The specifications list is non-exhaustive.

  • Worksheet File Format (From Lotus) December 1984
  • Open Document Format for Office Applications Version 1.3

The primary specifications for XLSX are:

  • ISO/IEC 29500 "Information technology — Document description and processing languages — Office Open XML File Formats"
  • ECMA-376 "Office Open XML file formats"

As some editions of ECMA-376 are identical to ISO specification editions, most of the public XLSX document community use the spec names interchangeably.

Open Specifications Promise

Lotus released their "Worksheet File Format" documentation into the Public Domain. Microsoft opted for the "Open Specifications Promise", a covenant not to sue. The documentation that falls under the promise are listed below.

Specifications (click to show)
  • MS-CFB: Compound File Binary File Format
  • MS-CTXLS: Excel Custom Toolbar Binary File Format
  • MS-EXSPXML3: Excel Calculation Version 2 Web Service XML Schema
  • MS-ODATA: Open Data Protocol (OData)
  • MS-ODRAW: Office Drawing Binary File Format
  • MS-ODRAWXML: Office Drawing Extensions to Office Open XML Structure
  • MS-OE376: Office Implementation Information for ECMA-376 Standards Support
  • MS-OFFCRYPTO: Office Document Cryptography Structure
  • MS-OI29500: Office Implementation Information for ISO/IEC 29500 Standards Support
  • MS-OLEDS: Object Linking and Embedding (OLE) Data Structures
  • MS-OLEPS: Object Linking and Embedding (OLE) Property Set Data Structures
  • MS-OODF3: Office Implementation Information for ODF 1.2 Standards Support
  • MS-OSHARED: Office Common Data Types and Objects Structures
  • MS-OVBA: Office VBA File Format Structure
  • MS-XLDM: Spreadsheet Data Model File Format
  • MS-XLS: Excel Binary File Format (.xls) Structure Specification
  • MS-XLSB: Excel (.xlsb) Binary File Format
  • MS-XLSX: Excel (.xlsx) Extensions to the Office Open XML SpreadsheetML File Format
  • XLS: Microsoft Office Excel 97-2007 Binary File Format Specification
  • RTF: Rich Text Format

Other Resources

  • ISBN 1556155212 "Excel Software Development Kit Version 4"
  • ISBN 1556156324 "Excel Developer's Kit Version 5"