Collabora Online

Last reviewed Sep 13, 2026 · 837 words

The Collabora Online decision is not whether, it is which of the two installs. Nextcloud offers a one-click built-in CODE server that works on x86-64, takes 2 minutes, and is fine for 1 to 3 people editing occasionally. A separate collabora/code container takes an hour with the reverse proxy, needs 2 GB of RAM, and is the only version I would put in front of a family or a team. Everything else in this guide is about the second one, because the first one needs no guide.

Collabora is a WOPI editor with no storage, no accounts, and no front page. Nextcloud, Seafile, or another file platform opens a document in an iframe and Collabora renders it with the LibreOffice engine. That is why it is filed under document management rather than as a standalone office suite.

The container behind a reverse proxy

The four environment variables below are the entire difference between a working install and a blank iframe:

services:
  collabora:
    image: collabora/code:latest
    environment:
      - aliasgroup1=https://cloud.example.com:443
      - extra_params=--o:ssl.enable=false --o:ssl.termination=true
      - dictionaries=en_GB en_US de_DE
      - username=admin
      - password=change-me
    ports:
      - "127.0.0.1:9980:9980"
    cap_add:
      - MKNOD
    restart: unless-stopped

aliasgroup1 is the list of file platforms permitted to open documents; a Nextcloud whose URL does not match it is refused, and the refusal shows up as nothing at all in the browser. extra_params tells Collabora that TLS terminates at your proxy so it speaks plain HTTP on 9980. The proxy then serves office.example.com over HTTPS and must pass WebSocket upgrades through, since editing sessions are WebSockets; Caddy does this by default, and nginx needs the Upgrade and Connection headers set on the location. Then in Nextcloud, install the Nextcloud Office app and set the server URL to https://office.example.com.

Why documents open blank, in the order I would check

Almost every failure is one of four things. One: the aliasgroup1 value does not match the Nextcloud URL exactly, including scheme and port. Two: DNS. Nextcloud must resolve office.example.com and Collabora must resolve cloud.example.com, from inside their containers, and on a LAN with a public domain that usually means split DNS or an extra_hosts entry; hairpin NAT failing silently is the classic cause. Three: WebSockets blocked at the proxy, which gives you a document that loads and never becomes editable. Four: Nextcloud's own list of permitted WOPI request sources under the Office settings, which needs the Collabora container's IP if you have restricted it. The admin console at https://office.example.com/browser/dist/admin/admin.html (using the username and password above) shows live sessions and memory, and is the fastest way to confirm whether Collabora is seeing requests at all.

Memory is per open document, and fonts are per install

The 2 GB minimum is honest. Each open document is a LibreOffice process of tens of megabytes, and 10 people with 2 documents each pushes past 1.5 GB before caching. On a shared box, give it a memory limit so a runaway spreadsheet does not take Nextcloud down with it. Fonts are the other surprise: the container ships a modest set, so a colleague's .docx in Calibri reflows on open. You can add fonts to the container or configure a remote font source through Collabora's settings, and it is worth doing before the first complaint rather than after.

Collabora or ONLYOFFICE

Both plug into the same Nextcloud, and the honest split is this. ONLYOFFICE Docs has better fidelity with Microsoft formats and an interface that Office users recognise, and its free build caps simultaneous connections at 20. Collabora is fully open-source under MPL-2.0, handles ODF and the long tail of formats the LibreOffice engine knows, and its CODE build has no hard connection cap, though it is positioned for small groups and the paid Collabora Online is the supported version for scale. If your users live in .docx all day and expect pixel-perfect tracked changes, ONLYOFFICE; if you care about open formats, licensing, or run anything other than Nextcloud, Collabora. Both are far better than the Google Docs replacement most people imagine, and neither is as fast as Google Docs on a slow connection.

What I'd do

A dedicated collabora/code container with the four environment variables above, behind the same reverse proxy as Nextcloud, on a box with at least 4 GB total so Nextcloud and Collabora do not fight. Split DNS from day one so the two hostnames resolve internally. The built-in CODE server only as a demo or for a single user who edits once a week. Memory limit set, fonts added, admin console bookmarked. Run like that it gives a household or a small team real collaborative editing on their own files, which is the point of running Nextcloud in the first place.