by IANUSTEC
Migrating away from the cloud shouldn't mean losing your data. Nextcloud has everything Google does — and more.
IANUSTEC believes leaving Big Tech infrastructure should be easy. We build open-source Nextcloud addons that bridge the gap between Google / Microsoft services and self-hosted alternatives — so companies can migrate at their own pace, without losing productivity.
This app is our Google Calendar bridge: it keeps every user's Nextcloud calendar in perfect sync with Google Workspace, bidirectionally, without any per-user configuration.
| Bidirectional sync | Events flow both ways — Nextcloud ↔ Google — with last-modified-wins conflict resolution |
| Domain-wide, zero per-user setup | One Service Account impersonates every user in the domain automatically |
| All calendars | Every calendar per user is synced, matched by display name |
| Incremental sync | Uses Google sync tokens and Nextcloud CTags — only changed events are transferred |
| Sync from date | Optionally limit import to events on or after a specific date |
| Sync direction control | Choose one or both directions independently from the admin UI |
| Meet links & locations | Google Meet conference links and event locations are preserved |
| Live progress UI | Admin panel shows per-user sync status in real time |
| Automatic & manual sync | Runs on a configurable cron interval; "Sync Now" button for immediate execution |
| Smart skip | Users outside the domain, without a Google Workspace license, or without calendars are silently skipped |
- Nextcloud 27–32 with DAV app enabled
- Google Workspace account with admin access
- Google Cloud Service Account with Domain-Wide Delegation
- PHP 8.1+ with
jsonandcurlextensions
Follow these steps once, as a Google Workspace admin.
Go to Google Cloud Console → APIs & Services → Library → search for Google Calendar API → Enable.
IAM & Admin → Service Accounts → Create Service Account.
Give it a name (e.g. nextcloud-calendar-sync). No roles are needed.
Open the Service Account → Details tab → check Enable G Suite Domain-wide Delegation → Save.
Service Account → Keys tab → Add Key → Create new key → JSON.
Save this file — you will upload it in the Nextcloud admin panel.
Go to admin.google.com → Security → API Controls → Domain-wide delegation → Add new:
| Field | Value |
|---|---|
| Client ID | The numeric client_id from the JSON key file |
| Scopes | https://www.googleapis.com/auth/calendar |
Click Authorize. Allow up to 10 minutes for propagation.
git clone https://github.com/ianustec/nextcloud-google-calendar-sync
cd nextcloud-google-calendar-sync
./deploy.sh k8s <namespace> <deployment>
# Example
GOOGLE_WORKSPACE_DOMAIN=yourdomain.com ./deploy.sh k8s my-namespace nextcloudgit clone https://github.com/ianustec/nextcloud-google-calendar-sync
cd nextcloud-google-calendar-sync
./deploy.sh docker <container-name>
# Example (container name from docker-compose.yml)
GOOGLE_WORKSPACE_DOMAIN=yourdomain.com ./deploy.sh docker nextcloudThe container name is the value of container_name in your docker-compose.yml, or the name shown by docker ps.
git clone https://github.com/ianustec/nextcloud-google-calendar-sync
cd nextcloud-google-calendar-sync
./deploy.sh local /var/www/html
# If occ requires root
GOOGLE_WORKSPACE_DOMAIN=yourdomain.com sudo ./deploy.sh local /var/www/nextcloudAll three modes handle composer dependencies, file copy, occ app:enable, migrations (occ upgrade), and web server reload automatically.
Open Nextcloud Admin → Additional settings → Google Workspace Calendar Sync.
| Setting | Description |
|---|---|
| Enable sync | Master switch. Disabling stops both cron and manual sync. |
| Sync direction | Google → Nextcloud: import Google events into NC. Nextcloud → Google: push NC events to Google. Both can be active simultaneously. |
| Google domain | Your Workspace domain (e.g. ianustec.com). Only users matching this domain are synced. |
| Sync interval | How often the background job runs, in minutes. Default: 15. |
| Email suffix | If Nextcloud usernames are not full email addresses (e.g. m.mazza instead of m.mazza@domain.com), set this to @domain.com to build the impersonation address. |
| Sync events from date | Only events on or after this date are imported from Google. Leave empty to sync all events. |
| Service Account JSON key | Upload the JSON file downloaded in step 4. Stored encrypted. |
After saving, click Test connection — it will attempt to list calendars for your own account and confirm the SA is correctly authorized.
Click Sync Now to immediately run a full sync for all users. A live table shows each user's status (Synced / Skipped / Failed) as it progresses.
┌─────────────────────────────────────────────────────┐
│ Nextcloud Admin UI (admin.js / AdminSettingsController) │
│ "Sync Now" → sequential per-user AJAX calls │
└────────────────────┬────────────────────────────────┘
│
▼
┌─────────────────────────────────────────────────────┐
│ SyncEngine::syncUser(userId) │
│ 1. List NC calendars (CalDavBackend) │
│ 2. List Google calendars (SA impersonation) │
│ 3. Match pairs by display name │
│ 4. For each pair → syncCalendarPair() │
│ a. Google→NC: create/update/delete NC events │
│ b. NC→Google: push new/changed NC events │
│ c. Conflict: last-modified wins │
│ 5. Save sync tokens + etags in mapping tables │
└─────────────────────────────────────────────────────┘
│
┌──────────┴──────────┐
▼ ▼
┌──────────────────┐ ┌──────────────────────────┐
│ CalDavBackend │ │ Google Calendar API v3 │
│ (Nextcloud DAV) │ │ (Service Account + DWD) │
└──────────────────┘ └──────────────────────────┘
Calendar matching: calendars are paired by display name. If no match is found, the primary Google calendar is paired with the first Nextcloud calendar.
Event mapping: two database tables (oc_neura_gcal_calendar_mapping, oc_neura_gcal_event_mapping) track which NC event UID corresponds to which Google event ID, enabling incremental sync.
Skip logic: users are silently skipped if they are outside the configured domain, don't have a Google Workspace Calendar license (notACalendarUser), or have no Nextcloud calendars. They appear as "Skipped" in the UI.
Migrations run automatically on occ upgrade after app enable. Two tables are created:
oc_neura_gcal_calendar_mapping— NC ↔ Google calendar ID pairs with sync tokensoc_neura_gcal_event_mapping— NC event UID ↔ Google event ID pairs with etags
# Reset sync state for a user (forces full re-sync on next run)
psql -c "UPDATE oc_neura_gcal_calendar_mapping SET google_sync_token = NULL WHERE user_id = 'user@domain.com';"
# Clear all events for a calendar (get calendarid from oc_calendars)
psql -c "DELETE FROM oc_calendarobjects WHERE calendarid = <id>;"
psql -c "DELETE FROM oc_neura_gcal_event_mapping WHERE nc_calendar_id = '<id>';"
psql -c "UPDATE oc_neura_gcal_calendar_mapping SET google_sync_token = NULL WHERE nc_calendar_id = '<id>';"Pull requests are welcome. Please open an issue first for significant changes.
This project is part of IANUSTEC's open-source initiative to help companies migrate from Google and Microsoft to self-hosted infrastructure.
GNU Affero General Public License v3.0 — © 2026 IANUSTEC s.r.l.