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Office Open XML

Office Open XML Document
The OOXML Document icon, as appears on the Microsoft OneDrive web service
Filename extension
.docx, .docm
Internet media type
Developed byMicrosoft, Ecma, ISO, IEC
Initial release7 December 2006; 17 years ago (2006-12-07)
Latest release
4th edition
26 October 2016; 7 years ago (2016-10-26)
Type of formatDocument file format
Extended fromXML, DOC, WordProcessingML
StandardECMA-376, ISO/IEC 29500
Open format?Yes[2]
WebsiteECMA-376, ISO/IEC 29500-1:2012
Office Open XML Presentation
Filename extension
.pptx, .pptm
Internet media type
Developed byMicrosoft, Ecma, ISO, IEC
Initial release7 December 2006; 17 years ago (2006-12-07)
Latest release
3rd edition
29 June 2011; 13 years ago (2011-06-29)
Type of formatPresentation
Extended fromXML, PPT
StandardECMA-376, ISO/IEC 29500
Open format?Yes
WebsiteECMA-376, ISO/IEC 29500:2008
Office Open XML Workbook
Filename extension
.xlsx, .xlsm
Internet media type
Developed byMicrosoft, Ecma, ISO, IEC
Initial release7 December 2006; 17 years ago (2006-12-07) (as Microsoft Open XML)
Latest release
3rd edition
29 June 2011; 13 years ago (2011-06-29)
Type of formatSpreadsheet
Extended fromXML, XLS, SpreadsheetML
StandardECMA-376, ISO/IEC 29500
Open format?Yes
WebsiteECMA-376, ISO/IEC 29500:2008

Office Open XML (also informally known as OOXML)[3] is a zipped, XML-based file format developed by Microsoft for representing spreadsheets, charts, presentations and word processing documents. Ecma International standardized the initial version as ECMA-376. ISO and IEC standardized later versions as ISO/IEC 29500.

Microsoft Office 2010 provides read support for ECMA-376, full support for ISO/IEC 29500 Transitional, and read support for ISO/IEC 29500 Strict.[4] Microsoft Office 2013 and later fully support ISO/IEC 29500 Strict,[5] but do not use it as the default file format because of backwards compatibility concerns.[6]


In 2000, Microsoft released an initial version of an XML-based format for Microsoft Excel, which was incorporated in Office XP. In 2002, a new file format for Microsoft Word followed.[7] The Excel and Word formats—known as the Microsoft Office XML formats—were later incorporated into the 2003 release of Microsoft Office.

Microsoft announced in November 2005 that it would co-sponsor standardization of the new version of their XML-based formats through Ecma International as "Office Open XML".[8][9] The presentation was made to Ecma by Microsoft's Jean Paoli and Isabelle Valet-Harper.[10][11]

Standardization process

Microsoft submitted initial material to Ecma International Technical Committee TC45, where it was standardized to become ECMA-376, approved in December 2006.[12]

This standard was then fast-tracked in the Joint Technical Committee 1 of ISO and IEC. After initially failing to pass, an amended version of the format received the necessary votes for approval as an ISO/IEC Standard as the result of a JTC 1 fast-tracking standardization process that concluded in April 2008.[13] The resulting four-part International Standard (designated ISO/IEC 29500:2008) was published in November 2008[14] and can be downloaded from the ITTF.[15] A technically equivalent set of texts is published by Ecma as ECMA-376 Office Open XML File Formats—2nd edition (December 2008); they can be downloaded from their website.[16]

The ISO/IEC standardization of Office Open XML was controversial and embittered,[17] with much discussion both about the specification and about the standardization process.[18] According to InfoWorld, "OOXML was opposed by many on grounds it was unneeded, as software makers could use OpenDocument Format (ODF), a less complicated office software format that was already an international standard."[17] The same InfoWorld article reported that IBM (which supports the ODF format) threatened to leave standards bodies that it said allow dominant corporations like Microsoft to wield undue influence. The article further says that Microsoft was accused of co-opting the standardization process by leaning on countries to ensure that it got enough votes at the ISO/IEC for Office Open XML to pass, although it does not specify exactly who accused Microsoft.[17]


Under the Ecma International code of conduct in patent matters,[19] participating and approving member organizations of ECMA are required to make their patent rights available on a reasonable and non-discriminatory (RAND) basis.

Holders of patents which concern ISO/IEC International Standards may agree to a standardized license governing the terms under which such patents may be licensed, in accord with the ISO/IEC/ITU common patent policy.[20]

Microsoft, the main contributor to the standard, provided a covenant not to sue[21] for its patent licensing. The covenant received a mixed reception, with some like the Groklaw blog criticizing it,[22] and others such as Lawrence Rosen, (an attorney and lecturer at Stanford Law School), endorsing it.[23]

Microsoft has added the format to their Open Specification Promise[24] in which

Microsoft irrevocably promises not to assert any Microsoft Necessary Claims against you for making, using, selling, offering for sale, importing or distributing any implementation to the extent it conforms to a Covered Specification [...]

This is limited to applications which do not deviate from the ISO/IEC 29500:2008 or Ecma-376 standard and to parties that do not "file, maintain or voluntarily participate in a patent infringement lawsuit against a Microsoft implementation of such Covered Specification".[25][26] The Open Specification Promise was included in documents submitted to ISO/IEC in support of the ECMA-376 fast-track submission.[27] Ecma International asserted that, "The OSP enables both open source and commercial software to implement [the specification]".[28]


The Office Open XML specification exists in several versions.

ECMA-376 1st edition (2006)

The ECMA standard is structured in five parts to meet the needs of different audiences.[16]

Part 1. Fundamentals
  • Vocabulary, notational conventions and abbreviations
  • Summary of primary and supporting markup languages
  • Conformance conditions and interoperability guidelines
  • Constraints within the Open Packaging Conventions that apply to each document type
Part 2. Open Packaging Conventions
  • The Open Packaging Conventions (OPC), for the package model and physical package, is defined and used by various document types in various applications from multiple vendors.
  • It defines core properties, thumbnails, digital signatures, and authorizations & encryption capabilities for parts or all of the contents in the package.
  • XML schemas for the OPC are declared as XML Schema Definitions (XSD) and (non-normatively) using RELAX NG (ISO/IEC 19757-2)
Part 3. Primer
  • Informative (non-normative) introduction to WordprocessingML, SpreadsheetML, PresentationML, DrawingML, VML and Shared MLs, providing context and illustrating elements through examples and diagrams
  • Describes the custom XML data-storing facility within a package to support integration with business data
Part 4. Markup Language Reference
  • Contains the reference material for WordprocessingML, SpreadsheetML, PresentationML, DrawingML, Shared MLs and Custom XML Schema, defining every element and attribute including the element hierarchy (parent/child relationships)
  • XML schemas for the markup languages are declared as XSD and (non-normatively) using RELAX NG
  • Defines the custom XML data-storing facility
Part 5. Markup Compatibility and Extensibility
  • Describes extension facilities of OpenXML documents and specifies elements & attributes through which applications can operate across different extensions.

Later versions of the ECMA-376 standard are aligned and technically equivalent to the corresponding ISO standard.

ISO/IEC 29500:2008

The ISO/IEC standard is structured into four parts:[29] Parts 1, 2 and 3 are independent standards; for example, Part 2, specifying Open Packaging Conventions, is used by other file formats including XPS and Design Web Format. Part 4 is to be read as a modification to Part 1, which it requires.

A technically equivalent set of texts is also published by Ecma as ECMA-376 2nd edition (2008).

Part 1. Fundamentals & Markup Language Reference
Consisting of 5560 pages, this part contains:
  • Conformance definitions
  • Reference material for the XML document markup languages defined by the Standard
  • XML schemas for the document markup languages declared using XSD and (non-normatively) RELAX NG
  • Defines the foreign markup facilities
Part 2. Open Packaging Conventions
Consisting of 129 pages, this part contains:
  • A description of the Open Packaging Conventions (package model, physical package)
  • Core properties, thumbnails and digital signatures
  • XML schemas for the OPC are declared using XSD and (non-normatively) RELAX NG
Part 3. Markup Compatibility and Extensibility
Consisting of 40 pages, this part contains:
  • A description of extensions: elements & attributes which define mechanisms allowing applications to specify alternative means of negotiating content
  • Extensibility rules are expressed using NVDL
Part 4. Transitional Migration Features
Consisting of 1464 pages, this part contains:
  • Legacy material such as compatibility settings and the graphics markup language VML
  • A list of syntactic differences between this text and ECMA-376 1st Edition

The standard specifies two levels of document & application conformance, strict and transitional, for each of WordprocessingML, PresentationML and SpreadsheetML, and also specifies applications' descriptions of base and full.

Compatibility between versions

The intent of the changes from ECMA-376 1st Edition to ISO/IEC 29500:2008 was that a valid ECMA-376 document would also be a valid ISO 29500 Transitional document;[30] however, at least one change introduced at the BRM—refusing to allow further values for xsd:boolean—had the effect of breaking backwards-compatibility for most documents.[31] A fix for this had been suggested to ISO/IEC JTC 1/SC 34/WG 4, and was approved in June 2009 as a recommendation for the first revision to Office Open XML.[32]

Applications capable of reading documents compliant to ECMA-376 Edition 1 would regard ISO/IEC 29500-4 Transitional documents containing ISO 8601 dates as corrupt.[33]

Application support

Some older versions of Microsoft Word and Microsoft Office are able to read and write .docx files after installation of the free compatibility pack provided by Microsoft,[34] although some items, such as equations, are converted into images that cannot be edited.[35]

Starting with Microsoft Office 2007, the Office Open XML file formats have become the default file format[36] of Microsoft Office.[37][38] However, due to the changes introduced in the Office Open XML standard, Office 2007 is not wholly in compliance with ISO/IEC 29500:2008.[39] Office 2010 includes support for opening documents of the ISO/IEC 29500:2008-compliant version of Office Open XML, but it can only save documents conforming to the transitional, not the strict, schemas of the specification.[40][41] Note that the intent of the ISO/IEC is to allow the removal of the transitional variant from the ISO/IEC 29500 standard.[41] Microsoft Office 2013 and later fully support ISO/IEC 29500 Strict,[5] but do not use it as the default file format because of backwards compatibility concerns.[6]

The ability to read and write Office Open XML format is, however, not limited to Microsoft Office; other office products are also able to read & write this format:

  • Collabora Online for Online, Mobile and Desktop apps are able to open and save Office Open XML files.[42]
  • SoftMaker Office 2010 is able to read and write DOCX and XLSX files in its word processor & spreadsheet applications.
  • LibreOffice is able to open and save Office Open XML files.[43]
  • Apache OpenOffice from version 3.0 can import Office Open XML files but not save them.[44] Version 3.2 improved this feature with read support even for password-protected Office Open XML files.[45][46][47]
  • The Go-oo fork of OpenOffice could also write OOXML files.
  • KOffice from version 2.2 and later was able to import OOXML files.
  • Calligra Suite is able to import Office Open XML files.
  • NeoOffice, an fork for OS X can import, supported saving to OOXML in 2017, NeoOffice was discontinued in 2024.
  • OnlyOffice, Online and Desktop editors compatible with OOXML and OpenDocument files

Other office products that offer import support for the Office Open XML formats include:

See also


  1. ^ a b c "Register file extensions on third party servers". Microsoft. Retrieved 2009-09-04.[permanent dead link]
  2. ^ Klaus-Peter Eckert; Jan Henrik Ziesing; Ucheoma Ishionwu. "Document Interoperability: Open Document Format and Office Open XML" (PDF). Fraunhofer Verlag. p. 90.
  3. ^ "The Document Foundation, LibreOffice and OOXML". The Document Foundation. Retrieved 2016-03-22.
  4. ^ "Overview of the XML file formats in Office 2010". Office 2010 Resource Kit. Microsoft. 5 August 2011.
  5. ^ a b "XML file name extension reference for Office 2013". Office 2013 Resource Kit. Microsoft. 26 December 2016.
  6. ^ a b "XLSX Strict (Office Open XML), ISO 29500-1:2008-2016". Library of Congress. Retrieved 2018-09-09.
  7. ^ Brian Jones (2007-01-25). "History of office XML formats (1998–2006)". MSDN blogs. Retrieved 2020-12-31.
  8. ^ "Microsoft Co-Sponsors Submission of Office Open XML Document Formats to Ecma International for Standardization". Microsoft. 2005-11-21.
  9. ^ Casson and Ryan, Open Standards, Open Source Adoption in the Public Sector, and Their Relationship to Microsoft’s Market Dominance
  10. ^ Microsoft hands over Office XML specs to Ecma
  11. ^ "Slides presented by the TC45 committee to Ecma International". Archived from the original on 2011-10-21. Retrieved 2011-06-08.
  12. ^ "Ecma International approves Office Open XML standard". Ecma International. 2006-12-07.
  13. ^ "ISO/IEC DIS 29500 receives necessary votes for approval as an International Standard". ISO. 2008-04-02.
  14. ^ ISO/IEC (2008-11-18). "Publication of ISO/IEC 29500:2008, Information technology—Office Open XML formats". ISO. Archived from the original on 2009-07-06. Retrieved 2008-11-19.
  15. ^ "Freely Available Standards". ITTF (ISO/IEC). 2008-11-18. Retrieved 2023-09-26.
  16. ^ a b "Standard ECMA-376". Retrieved 2009-05-19.
  17. ^ a b c Kirk, Jeremy (19 November 2008). "ISO publishes Office Open XML specification". InfoWorld. Retrieved 12 June 2010.
  18. ^ "Norwegian standards body implodes over OOXML controversy". Ars Technica. 3 October 2008.
  19. ^ "Code of Conduct in Patent Matters". Ecma International.
  20. ^ "ISO/IEC/ITU common patent policy".
  21. ^ "Microsoft's Open Specification Promise Eases Web Services Patent Concerns". September 12, 2006. Retrieved 2015-04-18.
  22. ^ "2 Escape Hatches in MS's Covenant Not to Sue". Groklaw. December 4, 2005.
  23. ^ Berlind, David (November 28, 2005). "Top open source lawyer blesses new terms on Microsoft's XML file format". ZDNet. Retrieved 2007-01-27.
  24. ^ "Microsoft Open Specification Promise". Microsoft. 2007-02-15. Retrieved 2015-04-18.
  25. ^ "Ecma formal publications". Ecma International. Ecma Standards and Technical Reports are made available to all interested persons or organizations, free of charge and licensing restrictions
  26. ^ "Microsoft Open Specification Promise".
  27. ^ "Licensing conditions that Microsoft offers for Office Open XML". 2006-12-20. Retrieved 2009-05-19.
  28. ^ "Microsoft Word — Responses to Comments and Perceived Contradictions.doc" (PDF). Retrieved 2009-09-16.
  29. ^ "ISO search for "29500"". International Organization for Standardization. 2009-06-05.
  30. ^ "Re-introducing on/off-values to ST-OnOff in OOXML Part 4". Archived from the original on 2009-06-26. Retrieved 2009-09-29.
  31. ^ "OOXML and Office 2007 Conformance: a Smoke Test". Archived from the original on 2010-04-28. Retrieved 2009-09-29.
  32. ^ "Minutes of the Copenhagen Meeting of ISO/IEC JTC1/SC34/WG4" (PDF). 2009-06-22. Archived from the original (PDF) on 2014-05-12. Retrieved 2009-09-29. page 15
  33. ^ "ISO/IEC 29500-4:2008/Draft Amd2:2011 - Draft - Information technology — Document description and processing languages — Office Open XML File Formats — Part 4: Transitional Migration Features - AMENDMENT 2". 2011-03-02. Archived from the original (PDF) on 2014-05-12. Retrieved 2011-04-04.
  34. ^ "Microsoft Office Compatibility Pack for Word, Excel, and PowerPoint 2007 File Formats (Version 3)". Microsoft. 2007-06-18. Retrieved 2018-06-23.
  35. ^ Open a Word 2007 document in an earlier version of Word - Word - Retrieved on 2013-07-17.
  36. ^ "Microsoft Expands List of Formats Supported in Microsoft Office". Microsoft. Retrieved 2008-05-21.
  37. ^ "Microsoft's future lies somewhere beyond the Vista by Evansville Courier & Press". Archived from the original on 2014-07-10. Retrieved 2009-05-19.
  38. ^ "Rivals Set Their Sights on Microsoft Office: Can They Topple the Giant? - Knowledge@Wharton". Retrieved 2009-05-19.
  39. ^ Andy Updegrove (21 May 2008). "Microsoft Office 2007 to Support ODF — and not OOXML". Archived from the original on 2008-05-23. Retrieved 2009-05-19.
  40. ^ "ISO OOXML convener: Microsoft's format "heading for failure"". Ars Technica. 2 April 2010.
  41. ^ a b Brown, Alex (31 March 2010). "Microsoft Fails the Standards Test". Where is an end of it?. Alex Brown's weblog. Retrieved 23 June 2018.
  42. ^ "Collabora Online 6.4.0-released". 2 November 2020.
  43. ^ "LibreOffice OOXML". Retrieved 22 March 2012.
  44. ^ " 3.0 New Features". 2008-10-13. Retrieved 2009-10-24.
  45. ^ " 3.2 New Features". 2010. Retrieved 2010-11-13.
  46. ^ Scott Gilbertson (13 February 2010). "OpenOffice 3.2 - now with less Microsoft envy". The Register. Retrieved 18 Feb 2013. the ability to open password-protected Word, Excel, and PowerPoint files
  47. ^ "3.2.0 (build OOO320_m12) - Release Notes". Retrieved 18 Feb 2013. Import of password protected Microsoft Office XML files

Further reading

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Office Open XML
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