LibreOffice Calls Euro-Office a Microsoft Trojan Horse in Open-Source Clothing

The Document Foundation says the newly launched Euro-Office defaults to OOXML — Microsoft's proprietary format — making it a functional ally of the lock-in strategy it claims to oppose.

Written by Julian Park · Bureau Tech · Jun 19, 2026

The Format Default Is the Strategy

Euro-Office launched with a pitch tailor-made for the current moment: a European office suite for a continent increasingly anxious about its dependency on American software platforms. The Document Foundation isn't buying it.

The foundation, which oversees LibreOffice, has publicly accused Euro-Office of being a 'de facto ally' of Microsoft's lock-in strategy. The reason is straightforward: Euro-Office defaults to OOXML — Office Open XML, Microsoft's document format — rather than ODF, the Open Document Format that is both an ISO standard and the format LibreOffice defaults to.

This is not a minor configuration quibble. Format defaults are one of the most consequential decisions a productivity software maker can make, and they almost always reflect whose interests the product is actually serving.

Why Defaults Are the Whole Game

Most users never change default settings. That's not a behavioral quirk — it's a documented pattern that platform strategists have exploited for decades. When a product defaults to OOXML, documents created in it are natively compatible with Microsoft Office and subtly incompatible with everything else. Recipients without Microsoft software encounter friction. Over time, that friction becomes a switching cost, and switching costs are how lock-in compounds.

ODF exists precisely to break this dynamic. It's an open standard, maintained by OASIS, and adopted by the EU's own interoperability frameworks as the preferred format for government documents. A product that claims to advance European digital sovereignty — the ability of European institutions to operate independently of specific vendors — while defaulting to a Microsoft-controlled format is, at minimum, sending a contradictory signal.

The Document Foundation's framing is harsher than that: it's not a contradiction, it's a strategy.

Who Wins From This?

The incentive structure here isn't hard to read. Euro-Office benefits from positioning as an alternative to Microsoft while remaining frictionlessly compatible with Microsoft's format ecosystem. That compatibility makes adoption easier — IT departments don't have to retrain staff or convert document libraries. It also means Euro-Office never actually threatens Microsoft's format dominance.

Microsoft, meanwhile, gets a competitor that competes on price and branding while reinforcing OOXML as the universal default. That's a reasonable outcome for Redmond even if Euro-Office takes some market share.

The loser in this scenario is ODF adoption — and by extension, the broader project of format-level interoperability that genuine digital sovereignty requires.

The Open-Source Wrapper Problem

This episode illustrates a pattern worth naming: open-source code does not guarantee open-source outcomes. A product can be built on LibreOffice's codebase, carry open-source licensing, and still make configuration choices that serve proprietary ecosystem interests. The code is open; the defaults are not neutral.

The Document Foundation's accusation is pointed because it's structural, not personal. Euro-Office may have no formal relationship with Microsoft. It doesn't need one. If its defaults route users into OOXML dependency, the effect is the same.

For European policymakers and procurement officers who've been told that switching to a 'European' office suite satisfies digital sovereignty requirements, this is the detail worth scrutinizing. Sovereignty isn't in the logo. It's in the format dropdown.

Key takeaways

Euro-Office defaults to OOXML (Office Open XML), Microsoft's document format, rather than the open ODF (Open Document Format) standard — a choice The Document Foundation calls disqualifying for any product claiming to advance European digital independence.
LibreOffice's steward has publicly labeled Euro-Office a 'de facto ally' of Microsoft's lock-in strategy, a pointed accusation that reframes Euro-Office not as a competitor to Microsoft but as an enabler.
Format defaults are a well-documented lever in platform competition: users rarely change them, so whoever controls the default controls interoperability — and ultimately, switching costs.
The dispute exposes a recurring tension in the open-source ecosystem: products built on open-source code can still serve proprietary interests if their configuration choices funnel users toward closed standards.
For European governments and enterprises pursuing digital sovereignty — reducing dependency on U.S. tech vendors — the format a product defaults to is arguably more consequential than its branding.

FAQ

What is OOXML and why does it matter which format an office suite defaults to?

OOXML (Office Open XML) is the document format developed by Microsoft and used natively by Microsoft Office. While it was ratified as an ISO standard, it remains closely tied to Microsoft's implementation. When software defaults to OOXML, documents are optimized for Microsoft's ecosystem, creating compatibility friction with other software and reinforcing switching costs. ODF (Open Document Format) is the alternative open standard, maintained by OASIS and preferred by EU interoperability frameworks.

What is digital sovereignty and why is document format relevant to it?

Digital sovereignty refers to the ability of governments, institutions, or regions to operate their digital infrastructure without dependency on specific foreign vendors. Document format is directly relevant because if all official documents are stored in a format controlled by a single company, that company has structural leverage over the institutions using it — including the ability to change licensing terms, pricing, or compatibility.

Is Euro-Office built on LibreOffice's code?

The available reporting does not confirm the precise technical lineage of Euro-Office's codebase. The Document Foundation's objection is focused on Euro-Office's format defaults and market positioning, not on code provenance.

Has Euro-Office responded to The Document Foundation's accusations?

No public response from Euro-Office is cited in the available sourcing. Bureau will update this article if a substantive reply is issued.

Does the EU have a formal policy on document formats?

Yes. The European Interoperability Framework recommends ODF for government documents, and several EU member states have mandated or strongly encouraged ODF use in public administration. A product defaulting to OOXML sits in tension with those frameworks, even if it doesn't violate them outright.

Citations

LibreOffice brands Euro-Office a 'de facto ally' of Microsoft's lock-in strategyThe Document Foundation accuses Euro-Office of undermining digital sovereignty by defaulting to Microsoft's OOXML document format and labels it a 'de facto ally' of Microsoft's lock-in strategy.
The Register — Technology News FeedBureau secondary source confirming story publication and context via The Register's editorial feed.
OASIS Open Document Format for Office Applications (ODF) TCODF is maintained by OASIS as an open standard for office document interoperability, distinct from Microsoft's OOXML.