Why OOXML is not a standard format for office documents

Unfortunately, I keep reading about open-source software advocates who happily use Microsoft’s proprietary DOCX, XLSX and PPTX formats for their documents and therefore prefer proprietary software such as OnlyOffice to LibreOffice. Others write outrageous things such as: “OOXML is a standard format, and we have to accept it.”

I would therefore like to take this opportunity to clarify, once and for all, why OOXML has never been, is not, and will never be a standard format unless Microsoft decides to completely redesign its office applications.

I consider this impossible in light of past decisions, such as Excel’s inability to handle elements of the human genome properly. This forced the scientific community to change the names of these elements due to Microsoft’s refusal to fix an obvious Excel bug.

In other words, because of Microsoft, all of us citizens of the world have been affected by the change of the names of some elements of our genome, with all that this entails for scientific research and, consequently, for the treatment of genetic diseases. This is an enormously important fact that has not received sufficient publicity in the media, but it illustrates how willing Microsoft is to overlook everything for its own commercial interests.

But let’s get back to OOXML.

In theory, OOXML (Office Open XML) is an ISO/IEC standard (ISO/IEC 29500), despite heavy technical criticism being raised by many parties during the process and completely ignored by ISO/IEC. This shows that it is not a standard, let alone an open standard.

The following is a summary of these criticisms:

Complexity of specifications: the standard is extremely voluminous (~7,000 pages), making it virtually impossible for third parties to implement correctly. This contrasts sharply with competing standards such as ODF, which are much more concise.

Implementation inconsistencies: Microsoft Office applications do not implement the standardized version (ISO/IEC 29500 Strict), but use the “Transitional” variant, which includes compatibility features with legacy formats that contradict the stated goal of being a clean, modern, and above all open and standard format.

Proprietary dependencies: The specifications refer to several undocumented legacy behaviors of previous versions of Microsoft Office and require implementers to decode Windows-specific features to achieve compatibility.

Binary blob remnants: Despite being based on XML, OOXML incorporates binary data structures in many places, particularly for backward compatibility with legacy formats, and this compromises the transparency that XML should guarantee.

Platform-specific elements: The standard contains Windows-specific elements related to fonts, rendering, and other system behaviors that make any cross-platform implementation difficult or even impossible.

Controversy over the standardization process: The fast-track approval process adopted for OOXML by ISO/IEC was highly controversial, with allegations of procedural irregularities and vote manipulation raising legitimate doubts about the validity of the standard.

These issues meant that, although OOXML technically became a standard, it has always been a proprietary Microsoft format specification and not a truly vendor-neutral open standard.

In the coming weeks, I will explore some of the claims made in this post in detail, with all the relevant technical elements.

For now, anyone interested can take a look at this PDF presentation from 2018, referring to ISO/IEC 29500-1:2016 (and the corresponding ECMA 376), which lists some of the issues and provides technical details that clarify at least some of the claims.

ODF Advocacy - OOXML

Please be aware that some of the slides referring to ECMA 376 are related to an old version of the standard and as such may be obsolete. The presentation will be updated with references to the current version of ECMA 376.

LibreOffice 26.2 is here: a faster, more polished office suite that you control

We’re pleased to announce the release of LibreOffice 26.2, the newest version of the free and open source office suite trusted by millions of users around the world. This release makes it easier than ever for users to create, edit and share documents on their own terms. Designed for individuals and organizations alike, it continues to be a trusted alternative to proprietary office software.

LibreOffice 26.2 is focused on improvements that make a difference in daily work and brings better performance, smoother interaction with complex documents and improved compatibility with files created in other office software. Whether you’re writing reports, managing spreadsheets, or preparing presentations, the experience feels more responsive and reliable.

LibreOffice has always been about giving users control. LibreOffice 26.2 continues that tradition by strengthening support for open document standards, and ensuring long-term access to your files, without subscriptions, license restrictions, or data collection. Your documents stay yours – forever.

Behind this release there is a global community of contributors. Developers, designers, translators, QA testers, and volunteers from around the world worked together to deliver hundreds of fixes and refinements. Their efforts result in a suite that not only adds features, but also improves quality, consistency, and stability, release after release.

What’s New in LibreOffice 26.2

  • Markdown import and export features.
  • Improved performance and responsiveness across the suite, making large documents open, edit, and save more smoothly.
  • Enhanced compatibility with documents created in proprietary and open core office software, reducing formatting issues and surprises.
  • Refined user interface behavior for a cleaner, more consistent experience.
  • Expanded support for open standards, reinforcing long-term access to documents.
  • Hundreds of bug fixes and stability improvements contributed by the global LibreOffice community.

See the Release Notes for the full list of new features.

Florian Effenberger, Executive Director of The Document Foundation, says:

LibreOffice 26.2 shows what happens when software is built around users, not business models, and how open source software can deliver a modern, polished productivity suite without compromising user freedom. This release is about speed, reliability, and giving people control over their documents.

LibreOffice 26.2 is available for Windows, macOS, and Linux, and supports over 120 languages out of the box. It can be used at home, in businesses, schools, and public institutions, with no licensing fees and no vendor lock-in.

You can download LibreOffice 26.2 today from the official LibreOffice website. We invite users to try the new release, share feedback, and join the community helping shape the future of LibreOffice. If they are happy, they can donate to support the independence and the future development of the project.

Downloads: www.libreoffice.org/download

Donations: www.libreoffice.org/donate

About LibreOffice and The Document Foundation

LibreOffice is a free, private and open source office suite used by millions of people, businesses, and public institutions worldwide. It is developed by an international community and supported by The Document Foundation, an independent non-profit organization that promotes open standards, digital sovereignty and user choice.

LibreOffice 26.2 Press Kit: nextcloud.documentfoundation.org/s/eDiocN8Gak6jDKx

The philosophy behind ODF: openness, freedom and control

File formats are not usually the subject of philosophical debate because most users just want to open, save and share documents without any problems. However, the Open Document Format (ODF) is based on concepts that are much more important to users than might initially seem the case. ODF is not just a technical standard, but also a statement of openness, user freedom, and control over digital information.

Understanding this philosophy helps to explain why ODF exists, why it is still important, and why it is often cited as a reference in conversations about digital rights and long-term access.
In short, ODF is an open standard for office documents such as text files, spreadsheets and presentations, and it is the native format of LibreOffice. Unlike Microsoft Office and Microsoft 365 files, which use a proprietary format developed in secret in Redmond and controlled by Microsoft, ODF is developed and maintained through a completely transparent process.

This may seem like a technical detail, but it is an important fact that determines everything else.

Openness: no one owns your documents

The principle behind ODF is openness. The complete specifications are available to the public, and anyone can read, implement or create software based on them without asking for permission or paying licence fees.

This has concrete consequences:

  • Developers can create compatible software without facing legal barriers.
  • Organisations can adopt ODF without being tied to a single supplier.

Users can manage their own documents without having to use a specific company’s tools.

Openness is not idealism for its own sake, but rather it means transparency and durability. When a format is open, knowledge of how it works does not disappear if a company changes direction, raises prices, or stops producing software.

Documents created today should still be readable decades from now. ODF was designed with this long-term perspective in mind.

Freedom: choice without penalties

In the context of ODF, freedom is primarily about choice.

With proprietary formats, even a simple software update can lead to hidden costs because files may not open correctly, formatting may not work and some features may disappear. Over time, this can discourage users from abandoning software, even if better or cheaper options exist.

ODF counteracts this dynamic.

Since multiple applications support the same format, users can choose the tools that best suit their needs. For example, you can write a document in one programme, edit it in another, and store it in a standard, open format, safe in the knowledge that it will be compatible.

This is particularly important for public institutions, schools and governments. When documents need to be accessible to all, tying them to a single vendor’s software creates an unnecessary barrier that goes against the democratic principle of equality. ODF supports the idea that public information should be readable using freely available tools.

In this context, freedom does not imply hostility towards commercial strategies, but rather respect for every user’s right not to be discriminated against because of file format.

Control puts power in the hands of the user

Control is the most overlooked part of the ODF philosophy.

When you save a document in a proprietary format, you often have to rely on undocumented behaviour, hidden features, or licence terms that have simply been imposed without negotiation. The supplier decides how the format changes and which features remain accessible to which users.

ODF reverses this relationship.

In fact, a standard format that is openly governed cannot be changed unilaterally by a single organisation. All decisions are discussed, documented and agreed upon through a public, transparent process. This guarantees that users and organisations will not be affected by a company’s strategies or held hostage by changes to their data.

Control also manifests itself in smaller, everyday ways. For example:

  • ODF files can be inspected: they are actually ZIP archives containing XML text that can be read by anyone, even those unfamiliar with the technology.
  • Documents can be automated, validated or processed using open tools.
  • You can migrate archives without having to reverse engineer a closed format.

This type of control is essential for legal documents, scientific data, historical archives and any other data that must remain intact and accessible over time.

Is ODF still important today?

In the era of cloud-based editors and collaborative platforms, it is reasonable to ask whether ODF is still relevant.

The answer is yes, perhaps more than ever.

Moving an increasing number of documents online takes control away from users because the files reside on servers that they do not manage and are in formats that they neither understand nor control. They are also governed by licence terms that users almost always sign without reading and which can change at any time.

ODF also sets a benchmark when the cloud is used for storage because an open, standard format guarantees the integrity and accessibility of data, regardless of users’ level of expertise. Thus, ODF protects users from their own unawareness of the format issue.

ODF also acts as a silent check on market power, reminding the software ecosystem that users must be able to switch applications without losing access to their content, which must remain their property and under their complete control.

The ODF philosophy is practical, not abstract, and translates into tangible results: reduced barriers, longer-lasting documents and greater choice.

Users do not need to become experts in standards or understand the specifics of the files to take advantage of this. ODF guarantees them permanent ownership of their work and the ability to manage it at any time with the software they prefer. This frees them from any constraints imposed by a supplier or tool that they have not chosen freely.

In this sense, ODF is not just a format, but also a reminder that digital files should serve the people who create them — not the other way around.

State of the Project – Calendar Year 2025

Starting in January 2026, at the beginning of each quarter, i.e. in January, April, July and October, I will publish a slide deck with updated statistics on the LibreOffice project.

Unless there are specific requirements, the statistics will refer to the last 12 calendar months. Therefore, the January statistics will refer to the 2025 calendar year, while the next ones will refer to the period from April 2025 to March 2026, and so on.

All published information is available online for further processing. Links to data sources are on the penultimate slide, with some notes on data processing.

If you have any questions or suggestions, please write to me: my email address is on the last slide.

202512-stateoftheproject

 

Why open standards are extremely beneficial to end users

Whenever I talk to other technology users — including CTOs, CSOs and ICT managers, who in theory should have a certain level of expertise — I realise that most of them never consider standards when using applications, devices or websites.

Users just want everything to work, but they don’t realise the fundamental role that standards, especially open standards, play in making this happen. Open standards actually offer users a significant advantage over the proprietary solutions they use every day.

An open standard is a publicly available set of rules that govern how technology works. Anyone can use, develop or improve them. Examples include HTML for websites, USB for devices and PDF for documents. (And of course, the Open Document Format – ODF – as used by LibreOffice.) These are not owned by any company, and therefore benefit end users.

That’s why they’re important to you.

1. You are not tied in

Open standards reduce vendor lock-in. This means that users are not forced to use a single product or ecosystem from a single company to have control over their data and tools.

For example, documents saved in an open format can be managed with multiple applications. If you change your device or software, your files will still work. You can choose the best solution for you, rather than being forced to use what the supplier provides.

It’s easy to take this freedom for granted until it’s gone. Just ask the Windows 10 users who had to abandon working software and PCs due to Microsoft’s business strategies.

2. Better compatibility between devices and applications

Open standards enable different products to work together more seamlessly. For example, your phone can connect to any laptop, your browser can open any website and your headphones can connect to any device. None of this is accidental. It is the result of open, shared standards.

For end users, this means fewer headaches and less time spent troubleshooting or wondering why something ‘should work’ but doesn’t.

3. More competition and better products

When standards are open, more companies can use them. This increases competition.

Competition leads to better prices, more advanced features, and much faster growth. Instead of handcuffing users with proprietary formats, companies must earn their trust.

As users, you benefit from greater choice and improved quality throughout the entire value chain.

4. Longer data life

Proprietary formats can disappear. Companies may change direction, discontinue products or go out of business. Ask the Windows 10 users mentioned earlier for more information.

Open standards tend to last much longer because they are not tied to the business strategies of a single company. Even after decades, data stored in an open format remains accessible, convertible and preservable.

This is important if users want their photos, documents or work to survive for longer than the lifespan of a single product.

5. Better accessibility

Open standards are often designed with accessibility in mind or to facilitate the proper functioning of accessibility tools.

Screen readers, alternative input devices and assistive software all rely on consistent, documented rules. When standards are open, developers and accessibility experts can test, improve and adapt them.

The result is technology that works better for more users.

6. Greater transparency and trust

With open standards, the rules are visible. Anyone can examine, test and report on them.

This transparency helps to identify security issues earlier and reduces the risk of behaviour that only benefits one supplier going unnoticed. While open does not automatically mean secure, it does mean fewer black boxes.

Over time, this increases users’ trust in the technology.

7. A healthier technology ecosystem

Open standards encourage collaboration and combat fragmentation between products because developers can focus on improvements rather than reinventing the basics or figuring out how to work around closed systems.

A healthier ecosystem means faster innovation and fewer dead ends for users. Things evolve, but they don’t break all the time or at the whim of vendors who rely on planned obsolescence.

Summary

In short, open standards are not flashy and are rarely directly visible to users, but they quietly influence the reliability, flexibility and fairness of the technologies we use every day.

When standards are open, users have more control and choice and experience fewer surprises. And in the long run, these are significant advantages.

The Future of Open Standards and the Importance of ODF

Open standards don’t make headlines. Instead, they work quietly behind the scenes to define how information is created, shared and stored. However, as digital ecosystems become more complex and centralised, open standards are becoming increasingly important.

One of the best examples is the Open Document Format (ODF), the native format of LibreOffice documents.

Open standards in the evolving digital world

The current digital environment is characterised by certain trends, such as cloud platforms, subscription software, artificial intelligence-based tools, and tightly integrated ecosystems. While these tools are powerful, they also increase the lock-in effect exerted by Big Tech.

Open standards act as a counterbalance. They provide shared rules that anyone can implement to maintain system interoperability and user control. When a format is open, no single company can decide how information is stored or who has access to it.

With ever-increasing data volumes and documents being transformed into long-term digital archives, this independence is becoming critical.

ODF was designed with one simple goal: to enable users to read and edit documents on any platform and with any software at any time. This goal is still absolutely valid today.

Because ODF is openly specified and standardised, it allows for the coexistence of multiple tools. LibreOffice and other editors can all work with the same files. Even proprietary software can support ODF without facing legal barriers.

Looking to the future, this aspect is more important than ever. Documents are now inputs for automated workflows, archives for public documents and sources for analysis with artificial intelligence tools, not just files on a desktop. Open formats enable these uses without any constraints.

Government, politics and long-term access

The future of ODF looks particularly secure in the public sector.

Governments are responsible for documents that must remain accessible for decades. Using proprietary formats carries risks in this context: companies change strategy, products are withdrawn from the market (Windows 10 docet), and licences evolve. Open standards reduce this risk.

Since digital sovereignty and transparency are political priorities, ODF is perfectly aligned with these objectives, as it enables public institutions to choose their software freely and maintain consistent access to all data.

ODF in the era of cloud computing and artificial intelligence

Contrary to popular belief, standard and open document formats remain highly relevant in an era of cloud computing and artificial intelligence.

Cloud platforms store documents in the format chosen by the user. If the format is open, users can move, analyse, edit and reuse data across different systems. The XML-based structure of ODF files makes processing documents at the development level easier, which is a key aspect of automation and AI-based workflows.

Since artificial intelligence tools rely heavily on existing documents for training, summarisation and decision support, transparent formats offer a practical advantage as well as a philosophical one.

Future challenges

Open standards are not without their challenges. They require ongoing governance (responsibility of ODF Technical Committee), consistent implementation across tools (which is lacking, because of the strategy of proprietary and open core software, which are pushing users towards proprietary formats against the user’s own interests) and widespread adoption (which has not yet been achieved for the aforementioned reason). Users favour default choices, which are often proprietary, for convenience and lack of expertise.

The future of ODF, and of open standards more generally, depends on continued support from institutions, developers, and users who value openness, even when it is less visible.

Why the future favours open standards

The long-term trend is clear. As digital systems become more powerful, the cost of lock-in grows with them. Open standards offer a way to share innovation without giving up control.

ODF may not be flashy, but it represents a lasting idea: that documents belong to the people who create them rather than the software they use. In the future of open standards, this idea will be more important than ever.