Document Foundation criticizes Microsoft Office formats over lock-in

The Document Foundation, the organization behind LibreOffice, has renewed its criticism of Microsoft Office file formats, arguing that the files used across Word, Excel and PowerPoint keep organizations dependent on Microsoft’s software. The group’s complaint centers on Office Open XML, the standard behind .docx, .xlsx and .pptx files, and on Microsoft’s continued use of the OOXML Transitional variant.

TDF says the practical problem is that a format presented as open is not equally usable across competing office suites. According to the foundation, OOXML’s standardization at the International Organization for Standardization was “one of the most contested processes” in ISO history, and the version that emerged included both OOXML Transitional and OOXML Strict.

The distinction matters for vendors trying to interoperate with Microsoft Office. TDF says OOXML Strict removed most legacy issues, though not all of them. Microsoft, however, made OOXML Transitional the default and placed Strict lower in the save-options list, according to the foundation. TDF argues that this means the files used every day by large numbers of Office users are in the variant that Microsoft’s own applications handle best, while the cleaner version that rival software could more readily support is rarely used and has disappeared from some versions.

The foundation’s position is direct: it says a standard that only one implementation fully supports behaves, in practice, like a proprietary format with formal standardization attached. TDF also claims the OOXML specification, which spans thousands of pages, described Microsoft Office’s existing behavior rather than a format built for broad interoperability, including legacy behaviors, undocumented features and implementation details tied to Microsoft’s code.

Microsoft’s position was not included. The Register said it contacted the company about file formats and user lock-in, and that Microsoft acknowledged the question but had not responded.

Why the complaint matters for enterprise software buyers

The argument is not only about LibreOffice versus Microsoft Office. TDF is tying document formats to digital sovereignty, a priority for governments and large institutions that want less dependence on a single vendor. Its view is that documents meant to remain usable across systems and over long periods require deliberate choices about file formats, fonts and software from the start.

TDF points to the OpenDocument Format, used natively by LibreOffice, as an alternative. It also warns that proprietary fonts can create similar dependencies if support later disappears or if an organization needs to reproduce documents outside the original application stack.

The criticism lands against a hard operational reality. Many companies and public bodies already hold thousands or millions of documents in Microsoft Office formats, and replacing the tools and workflows around them is not a trivial procurement decision. PDF/A can help with archiving, but it does not solve the day-to-day need to edit, exchange and preserve working documents.

The looming end of Microsoft Publisher is cited as an example of what can happen when files depend on an application that falls out of support. For TDF, that is evidence that file formats are part of the risk profile of a software estate, not an afterthought.

Its broader claim is that institutions reinforce vendor dependency when they send documents created with proprietary software, proprietary formats and proprietary fonts. The foundation says digital sovereignty starts with recognizing that these are choices. For CIOs and procurement teams, the uncomfortable part is that the cheapest time to make those choices was usually before the document archive existed.

This story draws on original reporting from The Register.