Euro-Office is a browser-based office suite for collaborative editing of text, spreadsheet and presentation documents. Version 1.0 was released on 9 June 2026, licensed under AGPL, based on a fork of the OnlyOffice Document Server. The backing consortium is IONOS, Nextcloud, Eurostack, XWiki, OpenProject, Soverin, Abilian, BTactic, Open-Xchange and Office.eu. Target audience is not consumers but public administration, education, regulated industries and SMEs with a sovereignty requirement.

How does Euro-Office differ from Collabora Online and LibreOffice?

Collabora Online is the LibreOffice engine in the browser, ODF-first, and has been the default in Nextcloud for years. LibreOffice is the Document Foundation's desktop suite, also ODF-first. Euro-Office is an OnlyOffice fork with an OOXML default and focuses on compatibility with DOCX, XLSX and PPTX. Technically a different code base, a different rendering strategy and a different format default. In Nextcloud Hub 26 Spring, Euro-Office and Collabora Online are selectable alternatives under the umbrella brand Nextcloud Office.

Why is there a dispute over the OOXML default?

The Document Foundation published an open letter the day before the launch, criticising Euro-Office for saving DOCX, XLSX and PPTX by default. These formats are standardised as ISO/IEC 29500, but are de facto Microsoft-dominated and in many details under Microsoft's control. The Document Foundation argues that a sovereign suite with a Microsoft default undermines its own tool against format lock-in. The Euro-Office consortium justifies the choice on pragmatic grounds – over ninety percent of office documents in German public administration today are in OOXML.

Can I deploy Euro-Office productively today?

Yes, with caveats. On IONOS Managed Nextcloud, Euro-Office can be selected immediately after launch. The roll-out to IONOS Nextcloud Workspace is announced for summer. Office.eu integrates the suite directly. Self-hosted Nextcloud Hub 26 Spring ships Euro-Office as a server component. There are still gaps in very complex Excel functions, pivot visualisations and PowerPoint animations. For classic office communication, contract drafts, exam papers and minutes, the feature set covers real-world testing.

Is Euro-Office GDPR-compliant and CADA Level 3 ready?

Euro-Office as software is GDPR-compliant and contains no telemetry to US servers. But GDPR and CADA assessment depend on the operator, not on the product. Anyone running Euro-Office on infrastructure that is European in ownership and located in the EU can potentially fulfil Level 3 under the CADA proposal. Anyone running Euro-Office on Azure Frankfurt does not, because the operator itself is structured under US ownership. We covered the legal assessment of CADA and the sovereignty levels in a separate article.

Microsoft alternatives·Jun 16, 2026

Euro-Office 1.0 – the sovereign Microsoft 365 alternative in a technical hands-on review

Euro-Office 1.0 launched on 9 June 2026 as a European Microsoft 365 alternative. What the suite delivers technically and who should adopt it now.

europioneer Team

Euro-Office 1.0 – the sovereign Microsoft 365 alternative in a technical hands-on review

On 9 June 2026, Euro-Office 1.0 was released as GA – an AGPL-licensed fork of the OnlyOffice Document Server, backed by a ten-strong European consortium of IONOS, Nextcloud, Eurostack, XWiki, OpenProject, Soverin, Abilian, BTactic, Open-Xchange and Office.eu. The launch landed on the exact same day as the release of Nextcloud Hub 26 Spring, which integrates Euro-Office as a selectable alternative to Collabora Online. For the first time in years, the European open-source stack now has a second, parallel office engine in the browser – and therefore a real choice under the Nextcloud Office brand.

We break down what Euro-Office is technically, where the dispute over the OOXML default actually matters in practice, how the suite compares to Collabora Online and LibreOffice and how an SME, a school authority or a municipality can introduce Euro-Office cleanly in the second half of 2026.

What Euro-Office is technically

Euro-Office is a browser-based office suite with real-time collaboration for text, spreadsheet and presentation documents. The architecture:

Code base: Fork of the OnlyOffice Document Server version 8.x, continued under AGPL by the Euro-Office consortium.
Rendering: Server-side document rendering, client-side JavaScript frontend with canvas-based display. Unlike Collabora Online, which runs a LibreOffice engine in the background, Euro-Office ships its own office renderer written in C++ and JavaScript.
Format default: OOXML – DOCX, XLSX, PPTX. ODF is fully supported but not the default.
Integration: Native integration into Nextcloud Hub 26 Spring via the WOPI interface. Office.eu runs Euro-Office directly as a hosted variant. IONOS Managed Nextcloud enables Euro-Office with one click.
Licence: AGPL-3.0. Euro-Office is pure open source – anyone may run their own instances, every code change must be disclosed when offered publicly.

Anyone obtaining Euro-Office via IONOS or Office.eu gets it in a managed model. Anyone running Nextcloud Hub 26 Spring themselves installs Euro-Office as a server component alongside the existing Collabora Online and can switch the default per tenant.

The OOXML dispute – where it matters in practice

The day before the launch, the Document Foundation, custodian of LibreOffice, published an open letter sharply criticising the OOXML default. The core criticism in one sentence: a suite marching under a sovereignty banner should not choose a default format that is de facto controlled by Microsoft. Heise quoted the letter as "de facto an ally of Microsoft".

Technically the dispute is substantive. ISO/IEC 29500 is an open standard, but:

The practical reference implementation lives at Microsoft.
Microsoft regularly ships new sub-formats and extensions that non-Microsoft implementations have to catch up to.
Complex constructs in DOCX – SmartArt, new chart types, OOXML math – are often only partially supported in third-party implementations.

In practice this matters in two constellations:

ODF requirements: Public authorities with a council decision on ODF, schools under an ODF strategy or SMEs running an ODF line. Here the default format must be actively switched to ODT/ODS/ODP – per tenant, not across the whole installation.
Loss-free Microsoft interoperability: Anyone corresponding with clients or authorities expecting DOCX benefits from the OOXML default – most documents stay format-preserving.

The more important message for IT leadership: Euro-Office does not change the fact that the format default is a deliberate configuration decision. Both paths are viable.

The consortium – why the line-up matters

The ten backing organisations are not a coincidental alliance, they cover the entire stack:

Organisation	Role in the stack
IONOS	Hosting provider, German data centre, managed Nextcloud backend
Nextcloud	Platform into which Euro-Office is integrated
Eurostack	Consortium for European tech sovereignty
XWiki	Wiki backend, complements Euro-Office with knowledge management
OpenProject	Project and time management, complements office with planning
Soverin	Email provider, Dutch
Abilian	French open-source house, integrates Euro-Office into CRM and ERP
BTactic	Spanish open-source integrator
Open-Xchange	Email and groupware platform, German subsidiary
Office.eu	Direct sales of the hosted variant

Background on the overall strategy – we described the consortium logic in Eurostack – Europe's digital sovereignty strategy 2026. Against Microsoft 365, Euro-Office closes the last remaining gap in the sovereign stack: the in-browser office that European implementations had to date filled only with Collabora Online.

Euro-Office vs. Microsoft 365 – the honest comparison

Criterion	Euro-Office 1.0	Microsoft 365
Operating location	Customer choice, within the EU	Microsoft data centres, EU Data Boundary with telemetry residual access
CLOUD Act exposure	None – European ownership	Full – Microsoft Corporation US
CADA level	Up to Level 3 possible at a European operator	Level 1, Level 2 contested
Format default	OOXML, switchable to ODF	OOXML
Real-time collaboration	Yes, in the browser	Yes, in the browser and desktop
Desktop app	No, browser-based	Word, Excel, PowerPoint desktop
AI integration	Not in the 1.0 release	Copilot, with Flex Routing risk – see Microsoft Copilot Flex Routing
Licence cost	Open source, hosting fee	EUR 12.90/user/month upwards
Complex Excel features	Gaps in pivot and Power Query	Full feature set
PowerPoint animations	Limited	Full feature set

The table covers most of the evaluation axes a German IT lead realistically weighs today. The gaps in Excel Power Query and PowerPoint animations are documented. Anyone running a controlling team with pivot models or a marketing department with Keynote-style animations should not put Euro-Office in the first wave.

Who should adopt Euro-Office in 2026 {#target-groups}

SMEs with office communication and contract drafts

Classic office needs – contract drafts, offers, minutes, simple calculations. Euro-Office covers this in full. The cost comparison against Microsoft 365 yields five-figure annual savings for a 50-person SME, even after accounting for hosting, migration and training.

Schools and school authorities

Schools are increasingly migrating away from Microsoft 365 because state authorities in NRW, Hesse and Lower Saxony have published corresponding requirements – background in Microsoft 365 in schools. Euro-Office fills the office gap that, after the switch to Nextcloud, had only been filled by Collabora Online. For pupils, OOXML compatibility is a concrete benefit – they receive documents from internship placements, external courses and parents that are almost always DOCX-formatted.

Public authorities and municipalities under CADA preparation

Authorities preparing for the Cloud and AI Development Act and Sovereignty Level 3 need an office stack that reaches Level 3 at a European operator. Euro-Office on a German or European-owned hoster reaches Level 3. Microsoft 365 does not – regardless of region or EU Data Boundary.

Where Euro-Office does not fit today

Research departments with LaTeX integration, controlling departments with complex pivot models, creative departments with InDesign and Premiere workflows. These users stay on dedicated tools in the first wave. Euro-Office is an office suite, not an Adobe replacement.

How to introduce Euro-Office cleanly

The HowTo block above documents seven steps. The order matters: inventory, pilot tenant, careful pilot group, deliberate format default, migration filter, two-stage training, broad rollout. Anyone skipping step 4 risks a creeping OOXML entrenchment in their records. Anyone skipping step 5 misses the one to three percent of documents needing rework and creates frustration on rollout day.

Terms – briefly defined

Euro-Office: Browser-based office suite, AGPL-3.0, launched 9 June 2026. Fork of the OnlyOffice Document Server. Consortium of ten European open-source and hosting organisations.
OOXML: Office Open XML, ISO/IEC 29500. Format family for DOCX, XLSX, PPTX. De facto Microsoft-dominated, formally an open standard.
ODF: Open Document Format, ISO/IEC 26300. Format family for ODT, ODS, ODP. Native home of LibreOffice and Collabora.
Nextcloud Hub 26 Spring: Release version of the Nextcloud platform from 9 June 2026, integrating Euro-Office as a selectable office engine alongside Collabora Online.
Nextcloud Office: Umbrella brand for the office engines under Nextcloud. Currently selectable: Collabora Online and Euro-Office.
WOPI: Web Application Open Platform Interface, the interface through which Nextcloud integrates office backends.
AGPL-3.0: Licence requiring disclosure of code changes when offered publicly. Strongest copyleft licence for server software.

Where europioneer fits in

europioneer operates the European open-source stack as a managed hosted service – Nextcloud Hub 26 Spring including Euro-Office, Collabora Online selectable, Element on Matrix for chat, Open-Xchange for email, Keycloak for identity. Hosting in German and EU data centres without hyperscaler sub-processors. For the rollout of Euro-Office in an SME or school authority, we handle the inventory in step 1, the pilot in steps 2 and 3 and the user training in step 6 – with either an OOXML or an ODF default. Packages and prices at /en/pricing. Component overview of the European stack at /en/alternativen. Live view of Microsoft dependencies at /en/microsoft. Pilot conversation at /en/contact.

Conclusion

On 9 June 2026 the European open-source stack closed its last remaining office gap. Euro-Office is not a LibreOffice competitor but a second browser office engine alongside Collabora Online – with a different format default and a different code base. The Document Foundation's OOXML criticism is legitimate, but it is a configuration decision, not a dead end. For a German SME with classic office communication, for a school authority under an NRW directive and for a municipality preparing for CADA, Euro-Office is a productive Microsoft 365 alternative today. Anyone running a pilot in the second half of 2026 will have defensible findings for procurement by early 2027 – and a clear path away from the EUR 12.90-per-user-month lock-in.

Request a Euro-Office pilot →

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