Nextcloud Office: Collabora vs. ONLYOFFICE — Which to Pick?

If you run Nextcloud as a collaborative platform, an integrated office backend is unavoidable. The two established options are Collabora Online and ONLYOFFICE Docs — both self-hostable, both GDPR-friendly, both officially supported by Nextcloud GmbH. The only real question: which one fits your environment?

The short answer: if you live in ODF documents and want to stay LibreOffice-compatible, Collabora is usually the better fit. If you exchange .docx, .xlsx and .pptx files daily with customers, accountants or public authorities, you will appreciate the format fidelity of ONLYOFFICE. The detailed answer follows.

Architecture and Origin

Collabora Online is based on the LibreOffice core. It is essentially a headless LibreOffice streaming rendered tiles over a WebSocket into the browser. The editor itself runs server-side — every keystroke is processed on the server, and the result is pushed back to the client. Upside: absolute format compatibility with LibreOffice and ODF. Downside: higher CPU load on the server and noticeable latency for fast typists on slow connections.

ONLYOFFICE Docs takes a different route. The editor is a genuine browser application in HTML5/JavaScript that renders in the client’s browser. The server only handles the conversion layer (DocumentServer) and co-editing synchronization. The engine was built from scratch for OOXML, which explains the high fidelity with Microsoft formats. Downside: ODF files are internally converted to OOXML — complex LibreOffice templates can suffer during round-trips.

Format Compatibility in Practice

This is the single most important decision point. In our customer projects we consistently see that format problems cost more time than any server configuration. A rough classification:

Aspect	Collabora Online	ONLYOFFICE Docs
ODF (.odt, .ods, .odp)	Native, lossless	Conversion, occasional layout drift
OOXML (.docx, .xlsx, .pptx)	Good, but detail deviations possible	Very high fidelity, often identical to MS Office
Legacy (.doc, .xls, .ppt)	Excellent (LibreOffice heritage)	Solid but less robust
PDF export	LibreOffice PDF engine	Own engine, typically smaller files
Track Changes / comments	ODF native, OOXML with limits	Reliable in both formats
Spreadsheet formulas	Complete (Calc base)	Complete, MS-Excel syntax preferred
Macros	LibreOffice Basic (can be disabled)	Not supported

If you routinely deal with public authorities still shipping .doc files from the 2000s, Collabora wins on legacy handling. If your accountant hands you an .xlsx template with complex pivot tables, ONLYOFFICE wins.

Docker Deployment

Both products ship officially as Docker containers. In Proxmox-based environments we recommend a dedicated LXC container or a small VM for the office backend, separated from the Nextcloud application server.

A minimal compose setup for Collabora Online 24.04:

services:
  collabora:
    image: collabora/code:24.04.13.1.1
    container_name: collabora
    restart: unless-stopped
    environment:
      - domain=cloud\\.example\\.com
      - username=admin
      - password=CHANGE_ME
      - extra_params=--o:ssl.enable=false --o:ssl.termination=true
    ports:
      - "127.0.0.1:9980:9980"
    cap_add:
      - MKNOD

For ONLYOFFICE Docs 8.2 Community Edition:

services:
  onlyoffice:
    image: onlyoffice/documentserver:8.2.2
    container_name: onlyoffice
    restart: unless-stopped
    environment:
      - JWT_ENABLED=true
      - JWT_SECRET=CHANGE_ME_LONG_RANDOM
      - USE_UNAUTHORIZED_STORAGE=false
    ports:
      - "127.0.0.1:8080:80"
    volumes:
      - ./data:/var/www/onlyoffice/Data
      - ./logs:/var/log/onlyoffice

Both containers belong behind a reverse proxy with a valid certificate — Nginx, Caddy or HAProxy. For customer deployments we prefer HAProxy on OPNsense, because it bundles rate limiting and geo-filtering out of the box. WebSocket upgrade headers (Upgrade/Connection) must be passed through, otherwise the co-editing session collapses.

Resource Footprint and Scaling

Server load differs significantly. Collabora is CPU-hungry because every rendering operation runs server-side. Rule of thumb: one CPU core per five concurrently active editors, plus reserve. RAM demand is around 300–500 MB per active session.

ONLYOFFICE is noticeably lighter on rendering because the browser does the work. The DocumentServer itself needs about 2 GB RAM as a baseline plus roughly 50 MB per concurrently opened document. Conversion jobs (e.g. on save) briefly spike CPU load.

For a 30-person company either backend runs comfortably in a container with 4 vCPUs and 8 GB RAM. Beyond 100 users you should think about horizontal scaling: Collabora can coordinate multiple backend instances behind a load balancer, and ONLYOFFICE offers clustered operation with shared Redis and PostgreSQL from the Enterprise Edition upward.

Do not forget backup — even though the documents live in Nextcloud, the database and configuration layer of the office containers needs to be included in the backup plan.

Licensing and Enterprise Support

Both products come in a free and a commercial variant — and the details differ massively.

Collabora Online Development Edition (CODE) is free but not recommended for production: limited concurrent users, no support, irregular updates. Collabora Online (the commercial edition) is priced per user per year, typically in the low three digits for bundles of 25+ users. Included: support, LTS updates, no user limits.

ONLYOFFICE Docs Community Edition is free under AGPLv3 but officially supports only up to 20 concurrent connections without a commercial license. The Enterprise Edition is sold as a server license (not per user), tiered by number of concurrent connections. That can be economical for large deployments but more expensive than Collabora for small teams.

Important: the Nextcloud integration itself — the connector in the Nextcloud app store — is free with both products. What you pay for is the backend.

Everyday User Experience

After rollouts across several customers a clear picture emerges: users coming from Microsoft Office feel at home with ONLYOFFICE faster. The ribbon UI, the keyboard shortcuts, even the formula dialogs in the spreadsheet are very close to the Redmond original. The learning curve is correspondingly flat.

Collabora feels less familiar to the same audience at first — the menu bar recalls classic LibreOffice, the sidebar navigation is different. But if you already use LibreOffice on the desktop, or come from an open-standards world, you feel at home immediately. Co-editing experience is now mature on both — cursors are color-coded, conflicts are resolved server-side.

One aspect often overlooked: mobile use. ONLYOFFICE ships native apps for iOS and Android that connect cleanly to a Nextcloud account. Collabora offers responsive web views but no dedicated mobile apps. For customers with heavy mobile use, this is often the deciding factor.

Our Recommendation

There is no universal answer — but good rules of thumb:

• Public sector, associations, ODF-first environments: Collabora Online. ODF fidelity and the LibreOffice foundation are unbeatable and align with the strategic direction of these organizations.
• SMBs with MS-Office-heavy customers and partners: ONLYOFFICE Docs. OOXML fidelity spares you conversion loops and support tickets.
• Pure internal use with mixed formats: both work — let the team decide after a two-week pilot.

Whichever you choose: combining Nextcloud on Proxmox, a hardened Linux host and a clean reverse-proxy setup on OPNsense gives you an office platform that stands up to Microsoft 365 technically — with full data sovereignty in Germany.

DATAZONE Supports You

DATAZONE plans, migrates and operates Nextcloud environments including office backend for medium-sized companies across the German-speaking region. We deliver more than containers — backup concepts, reverse-proxy hardening, user training and managed-service contracts. If you are replacing your current cloud office solution or introducing Nextcloud from scratch, get in touch — we will show you openly in the first meeting which backend fits your format landscape best.