The Document Foundation, the organization behind the popular office suite LibreOffice, has once again expressed scathing criticism against Microsoft. The focus of dissatisfaction lies in the complexity and supposed restrictions imposed by Office file formats, such as DOCX, XLSX and PPTX, which significantly hinder the work of alternative software developers.
Maintaining compatibility with the Office and Microsoft suite formats represents one of the biggest challenges for teams looking to offer open source alternatives. Cada new version of LibreOffice, such as the recent 26.2, includes improvements dedicated to this interoperability, highlighting the continuous effort to overcome technical barriers.
The foundation’s complaints are not unprecedented; they highlight a persistent demand for a truly open specification for OOXML (Office Open XML). The organization argues that, although the name suggests openness, Microsoft’s practical implementation of the standard prevents true compatibility and collaboration between different software ecosystems.
Challenges in document interoperability
The task of developing a robust productivity suite, such as LibreOffice, is already intrinsically complex, involving multiple software and interconnected functionalities. However, the need to seamlessly interoperate with Microsoft Office formats adds an extra layer of difficulty that consumes the open source community’s valuable time and resources.
This difficulty does not arise from a lack of commitment on the part of LibreOffice developers, but rather from aspects inherent to the OOXML standard, as reiterated by The Document Foundation. The organization seeks not direct support from Microsoft, but a review of the way the standard is maintained and implemented, aiming for more fluid collaboration and a truly open documentation environment for everyone involved.
The complexity of the OOXML format
Office Open XML (OOXML) is the file format standard that underlies documents created in Microsoft Office, generating widely used extensions such as DOCX for Word, XLSX for Excel, and PPTX for PowerPoint. Apesar’s inclusion of the term “Open” in its full name, The Document Foundation and other industry observers have questioned the true open nature of this standard.
The main reason for this dispute lies in the extreme complexity of the OOXML specifications. The official documentation, which details how these formats work, spans around 7,000 pages, making their complete and accurate implementation by third-party software a Herculean task. Este Massive volume of information requires a disproportionate investment of time and expertise to be deciphered and applied correctly, creating a significant barrier to entry.
In addition to the extensive documentation, the way Microsoft applications implement OOXML is also a point of contention. Rather than strictly adhering to the ISO/IEC 29500 standardized version of Strict, Office software often uses a “Transitional” variation. Essa transitional version incorporates support for legacy formats, which paradoxically complicates working with resulting files in alternative suites rather than facilitating compatibility.
Crucial points of the foundation’s critique
The Document Foundation articulated a series of specific criticisms about OOXML, which serve as the basis for its argument against the name “open standard”. The organization points out that the format specifications are unnecessarily complex, resulting in extensive documentation that makes it impossible to implement efficiently by external developers.
One of the strongest arguments is that Microsoft Office applications do not follow the “Strict” version of the ISO/IEC 29500 documentation, which would be ideal for interoperability. Instead, they use a “Transitional” version, which maintains compatibility with older features. Embora may benefit users of legacy versions of
Impact on the open source community
The persistent difficulty in ensuring full compatibility with proprietary Microsoft formats imposes a considerable burden on the open source development community, including projects such as LibreOffice. Developers are forced to devote a disproportionate share of their resources and time to reverse engineering and trying to adapt to specifications that are neither fully transparent nor openly collaborative. Isso diverts talent and effort that could be used to innovate new features, improve the user experience and expand the free software ecosystem itself, instead of constantly chasing the changes and peculiarities of a single company’s formats. The result is an environment where genuine interoperability is constantly compromised, limiting user freedom of choice and competitiveness in the productivity suite market, in addition to perpetuating a scenario of “lock-in” to a single platform, as previously denounced by the foundation.
The history of friction between giants
The Document Foundation’s criticisms of Microsoft about Office’s formats are not an isolated episode, but part of a history of friction that spans years. The battle for interoperability in the productivity software market is long-standing and reflects differing views on what constitutes a truly open standard.
In July 2025, for example, the entity had already accused Microsoft of employing questionable tactics to “trap” users into the Office ecosystem. Essas tactics, according to the foundation, involve manipulating file formats and creating dependencies that make migration to other platforms difficult, even if these alternatives are open source and equally capable.
The free software community, in general, argues that document standards should be open, well documented and independent of specific vendors. Isso would ensure that any software could read and write them without difficulty, promoting competition and freedom of choice for users around the world.
The central issue is that Microsoft’s stance, by maintaining purposeful complexity and certain dependencies in its formats, is seen as an obstacle to this vision. Fundação argues that this creates an artificial barrier that disfavors innovation and the dissemination of open technologies.
Variations and limitations of the ISO standard
The The Document Foundation review emphasizes that Microsoft Office uses the “Transitional” version of OOXML instead of “Strict” (ISO/IEC 29500 Strict). Esta implementation choice is not merely technical, but strategic, as the “Transitional” version maintains compatibility with legacy features and artifacts from older versions of Office.
This reliance on proprietary or undocumented elements, many of which are understood only by Microsoft itself, creates a technical “black box.” Consequentemente, third-party software such as LibreOffice faces enormous difficulties in accurately replicating the rendering and behavior of these documents. Além Furthermore, the presence of specific Windows components within OOXML “Transitional” makes cross-platform implementations difficult or even impossible.
Perspectives on document standards
Despite continued criticism and calls from the open source community, there is no indication that Microsoft plans to make substantial changes to the OOXML format. The company appears content with the current dynamics, maintaining control over a widely used standard.
