Office Open XML (OOXML) is a family of XML-based file formats for word-processing documents, spreadsheets and presentations, published by Ecma International as ECMA-376 and by ISO and IEC as ISO/IEC 29500.[1][2] Alongside the standard, Microsoft publishes the Open Specifications documents, technical documents that describe protocols, file formats, computer languages and standards support in its products, and attaches copyright and patent terms to them, including two unilateral patent promises: the Open Specification Promise and the Community Promise.[8]
These instruments concern the rights needed to implement a file format in other software. They are not licences to Office software and do not change how Office is counted, bought or audited; those subjects are covered in Microsoft licensing and Microsoft 365 and online services. The article is relevant to licence managers mainly because it marks the boundary between a published format that anyone may implement, subject to stated conditions, and a licensed product that only a licensee may run.
History
Ecma International’s standard page lists five editions of ECMA-376: the first in December 2006, the second in December 2008, the third in June 2011, the fourth in December 2012 and the fifth, whose parts carry separate dates. Part 1 and part 4 of the fifth edition are dated December 2016, part 3 December 2015 and part 2 December 2021, and the page notes that only part 2 was adopted in the last edition. The standard was prepared by Ecma technical committee TC45 and carries the ISO/IEC number 29500.[1]
ISO/IEC 29500 is maintained by ISO/IEC JTC 1/SC 34. Part 1, in its fourth edition of November 2016, replaced the withdrawn ISO/IEC 29500-1:2012. ISO records that the 2016 edition was last reviewed and confirmed in 2022, so it remains current, and lists a replacement draft (ISO/IEC FDIS 29500-1) as under development.[2]
Microsoft’s own documentation tracks the standard. Its implementer notes for ECMA-376 are published as [MS-OE376], and the notes for the ISO/IEC 29500 text as [MS-OI29500]. The latter’s published version 25.0 is dated 2026-08-18, with a revision history running back to 2016, which shows that the notes are revised several times a year.[9][10]
Scope and definitions
The standard
ISO describes ISO/IEC 29500-1:2016 as defining a set of XML vocabularies for word-processing documents, spreadsheets and presentations. It states two goals: to represent faithfully the pre-existing corpus of documents produced by Microsoft Office applications from Office 97 to Office 2008, and to enable implementations by multiple vendors on multiple platforms. It also specifies requirements for Office Open XML consumers and producers, and it defines both strict and transitional conformance.[2]
Ecma’s page divides the standard into four parts: Fundamentals and Markup Language Reference (part 1), Open Packaging Conventions (part 2), Markup Compatibility and Extensibility (part 3) and Transitional Migration Features (part 4).[1]
The Open Specifications programme
Through the programme, Microsoft makes technical documents for interoperability with certain products available to view and download at no charge. They cover protocols, computer languages (VBA and XAML), standards support, and data portability, the last meaning the file formats created by Word, Excel, PowerPoint and Outlook and by SQL Server.[8] The implementer notes are one category. They explain how Office implements the standard, including areas where the product varies from or extends it, so that other implementers can interoperate.[11]
Copyright and patent notice
The Intellectual Property Rights Notice attached to Open Specifications documents has four elements:
| Element | What the notice says |
|---|---|
| Copyright | The documentation is covered by Microsoft copyrights, but readers may copy it to develop implementations, distribute portions in their implementations or their own documentation, and distribute included schemas, IDLs or code samples with or without modification |
| Trade secrets | Microsoft claims no trade secret rights in the documentation |
| Patents | Microsoft has patents that might cover implementations. The notice and the delivery of the documentation grant no patent licence, but a given document might be covered by the Open Specification Promise or the Community Promise. Written licences are available on request where it is not covered |
| Other rights | Reserved |
Source: Microsoft Intellectual Property Rights Notice for Open Specifications Documentation, as reproduced in [MS-OE376].[9]
Ecma International separately governs the copyright and patent terms of the standard text. Its default copyright notice permits copying and distribution and a limited set of derivative works, which includes works that implement the functionality of a specification in conformant products, for example by copying text wholly or partly.[13] Its Code of Conduct in Patent Matters asks participants to disclose patents that may be required to implement a standard and to declare that licences are available either free of charge or on reasonable and non-discriminatory terms; where a patent holder contributing technology makes no selection, the second, non-free option applies.[12]
The Open Specification Promise
Microsoft published the Open Specification Promise on 2006-09-12 and revised it on 2023-02-24. It states that Microsoft irrevocably promises not to assert any “Microsoft Necessary Claims” against anyone making, using, selling, offering for sale, importing or distributing an implementation, to the extent that it conforms to a Covered Specification.[3]
The text sets out these terms:
- Personal promise. It is made directly to each implementer, and the beneficiary acknowledges that no Microsoft rights are received through suppliers or distributors.
- Scope of claims. Necessary Claims are claims of Microsoft-owned or Microsoft-controlled patents that are necessary to implement only the required portions of the Covered Specification that are described in detail, not those merely referenced.
- Suspension. If the beneficiary files, maintains or voluntarily participates in a patent infringement suit against a Microsoft implementation of the same Covered Specification, the promise no longer applies to that beneficiary’s implementations of that specification.
- No assurances. The promise is not an assurance that Microsoft’s patents cover an implementation, that they are enforceable, or that the implementation avoids third-party patents or other third-party rights. No other rights are granted by implication, exhaustion or estoppel.
The covered list relevant to Office formats names ECMA-376 and the 2008, 2012 and 2016 versions of ISO/IEC 29500, together with the implementer notes [MS-OE376] and [MS-OI29500]. For the implementer notes the definition of necessary claims is adjusted to the information in the notes read together with the specification they apply to. The list also includes Microsoft’s Office file format extension specifications, for example [MS-DOCX], [MS-PPTX], [MS-XLSB] and [MS-OFFMACRO], the earlier Word, Excel and PowerPoint binary file format specifications, and the OpenDocument Format versions 1.0 to 1.3. Microsoft commits to apply the promise to future versions of the Open XML and OpenDocument specifications, for as long as it participates in their revision to completion.[3]
The Community Promise
The Community Promise, published on 2007-09-12 and revised on 2023-01-31, has a similar structure but a narrower condition: it protects an implementation only to the extent that it conforms to a Covered Specification and complies with all required parts of the mandatory provisions of that specification. Its definition of necessary claims includes the required elements of optional portions.[4]
Microsoft’s FAQ for the Community Promise adds several points. Nobody needs to sign or notify Microsoft; partial implementations are not covered; the promise does not extend to work beyond the covered specifications or to technology merely referenced in them; distributees, customers and vendors of an implementer can rely on the promise directly without sub-licensing; and copyrights in the specifications are not provided through the promise, because the copyright holder, a standards body or Microsoft, licenses them separately.[5]
The Community Promise list retrieved on 2026-10-08 covers ACPI tables, the C# language specification (Ecma-334 and ISO/IEC 23270), the Common Language Infrastructure (Ecma-335 and ISO/IEC 23271) and a range of internet protocol specifications, among others; it does not list the Office Open XML specifications, which are covered by the Open Specification Promise.[4]
Differences at a glance
| Question | Open Specification Promise | Community Promise |
|---|---|---|
| Published | 2006-09-12 | 2007-09-12 |
| Latest revision | 2023-02-24 | 2023-01-31 |
| Condition for protection | Implementation conforms, to the extent of conformance, to a Covered Specification | Implementation complies with all required parts of the mandatory provisions |
| Partial implementations | Aimed at developers who implement “all or part” of a covered specification | Not covered |
| Covers Office Open XML | Yes, as listed | Not in the list retrieved |
| Suspension on suing Microsoft | Yes, for the same Covered Specification | Yes, for any Covered Specification |
Sources: Open Specification Promise, Community Promise and Patent Promises and Patents pages.[3][4][5][6]
Relationship to licensing of Office file formats
Reading the instruments together shows what they do and do not decide.
What they cover. They address Microsoft patents and, for the documentation, Microsoft copyright. An implementer such as a third-party editor, converter or library that reads or writes Office Open XML can rely on the promise for Microsoft’s necessary patent claims in the required portions of the covered specification, and on the copyright notice for copying the documentation and its schemas.[3][9]
What they do not cover.
- The Office software. Neither promise grants rights in Microsoft’s software, services or trademarks. The Intellectual Property Rights Notice reserves all other rights.[9] Running Office, or an Office-compatible service, remains subject to the applicable product terms.
- Third-party rights. Both promises disclaim any assurance about third-party patents or other rights.[3][4]
- Referenced technology and unlisted versions. Claims on technology merely referenced in a specification are outside the promises, and a version that is not on a covered list is covered only if specifically added.[3][4]
- Patents outside the promises. Where Microsoft patents are not covered by either promise, Microsoft offers licences through separate programmes: the Microsoft Interoperability Program, the Workgroup Server Protocol Program and the Interoperability Principles Program.[6][7]
- Product behaviour. The standard is not a complete description of what Office writes. The implementer notes record where the product varies from or extends the specification, so a file produced by Office can contain constructs the standard does not define.[11]
Practical reading for licence managers. The promises run to implementers of the specifications and are expressly separate from Microsoft’s product terms.[3][9] Whether a clause in a customer’s executed agreement restricts analysing or replicating product functionality, and how it interacts with a published format, depends on that agreement and is not resolved here.
Relationship to other disciplines
Disputes over copyright in program structure, interfaces and data formats are discussed in SAS Institute v World Programming and Computer Associates v. Altai. General rules about what a licence grants are in Software license, and licences that allow implementation and redistribution of code in Open-source software licensing. The Community Promise FAQ notes that open source implementers, including those distributing under the GPL, can rely on the promise but should take their own advice on their particular legal environment.[5]
Out of scope
- Licensing, counting and audit of Microsoft Office, Microsoft 365 and Windows Server (see Microsoft licensing).
- Advice on whether a particular implementation conforms to a covered specification or infringes a patent.
- The OpenDocument Format as a standard, other than its appearance on Microsoft’s covered list.
- The text of the Microsoft Interoperability Program, Workgroup Server Protocol Program and Interoperability Principles Program licences, which Microsoft provides on request.