LibreOffice once again slams Microsoft for using "lock-in" with Office files

Published Jul 19, 2026, 4:02 AM EDT Simon is a Computer Science BSc graduate who has been writing about technology since 2014, and using Windows machines since 3.1. After working for an indie game studio and acting as the family's go-to technician for all computer issues, he found his passion for writing and decided to use his skill set to write about all things tech. Since beginning his writing career, he has written for many different publications such as WorldStart, Listverse, and MakeTechEasier. However, after finding his home at MakeUseOf in February 2019, he would eventually move on to its sister site, XDA, to bring the latest and greatest in Windows, Linux, and DIY electronics. Summary Microsoft's DOCX/XLSX/PPTX creates silent lock-in, claims LibreOffice. Proprietary features hide behaviors, break fidelity in third-party apps, and risk ruining long-term access. LibreOffice says people should choose open formats (ODF, PDF/A) to break free from Microsoft dependency. With Microsoft Office being one of the biggest productivity suites in the world, it's easy to assume that the file formats it uses are the only ones anyone really uses. However, The Document Foundation argues that it only happened because we don't use anything else. A new blog post on the LibreOffice website breaks down why using proprietary document formats is harmful and what people can do instead. LibreOffice calls Microsoft's document format practices a "lock-in" It believes open formats are the only way people can get digital sovereignty One of the founding members of The Document Foundation and handler of LibreOffice's PR and media relations, Italo Vignoli, took to the LibreOffice blog to call out Microsoft's practices with its Office application. The last time we saw Vignoli take to the stage, we saw him accusing Euro-Office of being just as bad as Microsoft with its practices. Vignoli's new post focuses entirely on Microsoft's strategy. He says that "the dominant format for office documents" is owned by Microsoft Office, particularly the DOCX, XLSX, and PPTX formats. The problem with these formats, Vignoli states, is that they "belong to Microsoft, are controlled by Microsoft and serve Microsoft’s interest." This makes it difficult for other formats to take hold. Vignoli explains his point by stating that open document formats don't hide anything. People developing their own apps can use the format to both read and write the document format with perfection. Meanwhile, proprietary formats such as Microsoft's "contain undocumented features, private extensions or behaviours" that developers can't fully adapt to. That means that a presentation that looks great in the source software comes out strange when rebuilt in a third-party app. This, Vignoli says, is a huge issue: This is “lock-in”: it is not a padlock, it is not a technical ban, it is not a contractual restriction, but a silent and persistent friction that makes any work outside the Microsoft ecosystem seem slightly off, slightly unreliable, slightly unprofessional — and ensures that the easiest route is to return to the tools that produce documents with the expected appearance. Vignoli claims this creates a huge issue with document preservation. If a Word document was saved in one version of Office, will it still be readable in 20 years? Microsoft has added legacy support to its software before, but the company can one day decide that it's not worth the effort anymore and cut it out. When that happens, you have old documents that are either jumbled or unable to be opened at all. Meanwhile, the Open Document Format (ODF) hides nothing. This allows documents to be read, saved, and stored in a way that anyone else can retrieve. In fact, Vignoli points to the PDF/A format for documents intended for permanent archiving, which uses an open standard that anyone can remake at any time. Vignoli finishes his blog post by saying that every time someone uses a proprietary format with proprietary software, they're helping perpetuate the dependency on the technology used to make it. Only when people decide to move away and use an open format can people break free of those restraints.