Calendar sync tool comparison

The best calendar sync tools 2026 – an honest comparison

OneCal, CalendarBridge, SyncGene, Reclaim.ai or Kalender Sync? We compare the most important providers honestly by features, price, privacy and hosting – so you find the right tool for your setup and use case.

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Intro

What matters in the comparison

Anyone using multiple calendars knows the problem: Google, Outlook and iCloud don't talk to each other. One double-booking later, you're asking "which sync tool should I pick?". The honest answer: it depends on what matters more to you – maximum feature set, lowest price or uncompromising European privacy.

Six factors decide:

Privacy & hosting – Where is your event data processed? Tools with US servers fall under US law (Cloud Act, FISA 702), even if they claim GDPR compliance.
Supported providers – Google, Outlook, iCloud are standard. Niche providers like GMX, WEB.DE, mailbox.org, KSuite (Infomaniak) or arbitrary iCal feeds are only found in a few tools. Kalender Sync supports 8 provider types – and is the only tool in this comparison with dedicated one-click GMX & WEB.DE integrations.
Sync mode & visibility – Copy "full details" or only show "busy"? This default reveals a lot about a tool's privacy philosophy.
Sync direction – One-way or both, selectable per connection?
Speed – Real-time (webhooks/push) or periodic polling (every 10–15 minutes)?
Price & limits – How many calendars per plan? How does it scale for teams?

Comparison table

At a glance

As of May 2026. Please verify pricing and features on the vendors' websites before purchasing.

Criterion	Kalender Sync	OneCal	CalendarBridge	SyncGene	Reclaim.ai
Vendor & location
Headquarters	Munich, DE	Tirana, AL	Chicago/Miami, US	(Azure-hosted)	US
Hosting	Germany (Hetzner)	AWS (us-east-1, USA)	US cloud	Microsoft Azure	US cloud
GDPR DPA	Available (Professional incl., otherwise on request)	Available (all plans)	Available	Available	Available
Privacy
Default visibility	Selectable per sync — default "busy" only (Free/Busy)	Configurable	Selectable at setup	Full details	Per-sync choice
Functionality
Supported providers	8 types incl. GMX & WEB.DE	Google, Outlook, iCloud	Google, Outlook, iCloud, ICS	Google, Outlook, iCloud, more	Primarily Google, Outlook
Sync speed	Real-time from Basic (Free: 30-min interval)	Real-time (iCloud up to 10 min)	Real-time	Periodic	Real-time
One-way / two-way	Both, per connection (two-way from Basic)	Both	Both	Both	Both
Booking links	—	Included	Included	Included	Included (AI-powered)
Share calendar (embed in someone else's)	Yes (Free: 1, Basic: 5, Professional: ∞)	—	ICS feeds only (no live sync)	Yes (via invitation)	—
Self-sync (multiple own calendars)	Yes, from Basic	Yes	Yes	Yes	Partial
AI access (MCP)	Yes – Claude & ChatGPT	—	Yes (all plans)	—	Yes (core feature)
Pricing
Permanently free plan	Yes (1 sharing)	No, 14-day trial	No, trial only	Limited on Free	Free plan limited
Entry price	Free / €5	$5 / user / month	from $4 / month (annual, 2 cals)	Free / paid	Free / $10
Entry value	3 accounts for €5	1 user for $5	2 calendars for $4	Limited	1 sync free

The seven tools at a glance

Which tool was built for what

Kalender Sync

The specialist for GDPR-compliant sync

Our tool

Hosting in Germany (Hetzner, Nuremberg), DPA available, three visibility levels per sync (Free/Busy by default).
8 provider types – Google, Microsoft Outlook/M365, Apple iCloud, GMX, WEB.DE, mailbox.org, Infomaniak kSuite and iCal feeds. The only tool in this comparison with dedicated one-click GMX & WEB.DE integrations – no manual CalDAV setup.
True live calendar sharing into other calendars – with three selectable visibility levels and a custom display name per sharing.
One sharing permanently included in the Free plan; syncing your own calendars starts on Basic with 3 accounts for €5/month.
No AI-scheduling overhead – but your own AI assistant (Claude, ChatGPT) gets controlled MCP access to your calendars.

For who: Tax advisors, coaches, schools, executives across multiple companies, AI agent integration with privacy needs.

OneCal

The all-rounder

Clean UX, multi-way sync, granular visibility control, native mobile apps.
AWS hosting – no EU hosting guarantee. iCloud sync up to 10-minute latency.

For who: International freelancers and consultants for whom US cloud hosting is uncritical.

Detailed comparison: Kalender Sync vs. OneCal

CalendarBridge

The veteran with AI integration

On the market since 2019, own patent on privacy-focused sync method, AI assistant included.
Headquartered in the US (Chicago/Miami), data subject to US law.

For who: US-oriented consultants wanting AI-assisted scheduling in their workflow.

Detailed comparison: Kalender Sync vs. CalendarBridge

SyncGene

The multi-sync generalist

Beyond calendars, also syncs contacts and tasks, runs on Microsoft Azure.
Azure hosting (US vendor), sync periodic instead of real-time, broad complexity. Transitioning to brand CiraHub.

For who: Individuals wanting to consolidate contacts and events across multiple devices.

Detailed comparison: Kalender Sync vs. SyncGene

Reclaim.ai

The AI planning assistant

Best AI planning on the market, priority-based scheduling, generous free plan, true two-way sync between Google and Outlook.
Calendar sync isn't the core feature, iCloud isn't supported directly (only via Google detour). US vendor.

For who: Solo pros and small teams wanting to integrate time-blocking and habits into their workflow.

Detailed comparison: Kalender Sync vs. Reclaim.ai

SyncDate

The fast EU sync

Hosts in Germany (Hetzner) like us, GDPR-compliant and privacy-first – very fast webhook sync for Google/Outlook and broad CalDAV support.
Young product from a small team; the contracting party (including for the DPA) is a Romanian S.R.L.; no sharing into other people's calendars.

For who: Technical users who want many CalDAV providers and maximum sync speed.

Detailed comparison: Kalender Sync vs. SyncDate

SyncThemCalendars

The fast Google Workspace add-on

Set up in a few clicks via the Google Workspace Marketplace, granular field-level privacy, strong reviews.
Data processing in the US, no free plan (7-day trial only), Google-centric, a two-way relationship consumes two syncs.

For who: Google Workspace teams who want a fast add-on and can live with US data processing.

Detailed comparison: Kalender Sync vs. SyncThemCalendars

All comparisons

All detailed comparisons

Kalender Sync compared head-to-head with every relevant tool on the market — honestly, including each side's strengths.

Show all 31 detailed comparisons

Recommendation

Which tool fits whom?

You want sync as a main discipline, not a side feature?: → Kalender Sync. The only pure sync specialist in this comparison – with hosting in Germany, selectable visibility (Free/Busy by default) and real live sharing into other people's calendars with three selectable visibility levels.
You're in the DACH region or have compliance requirements?: → Also Kalender Sync. A German company, hosting in Germany (Hetzner) and a DPA available (included in the Professional plan, otherwise on request). SyncDate also hosts in the EU, but your contracting party is a Romanian company.
You want a fast, affordable EU sync – but with a German contractual partner?: → Kalender Sync over SyncDate. Same EU hosting and privacy level, but as a German company with a DPA, German-language support and real live-sharing into other calendars.
You use GMX, WEB.DE, mailbox.org or KSuite?: → Kalender Sync. 8 provider types – Google, Microsoft Outlook/M365, Apple iCloud, GMX, WEB.DE, mailbox.org, Infomaniak kSuite and iCal feeds. The only tool in this comparison with dedicated one-click GMX & WEB.DE integrations – no manual CalDAV setup.
You want a Swiss-army knife with booking links and unified view, and a US vendor is fine?: → OneCal or CalendarBridge. Both offer sync + booking links + unified view from one tool.
You also need contacts and tasks in the sync?: → SyncGene (or CiraHub going forward).
You want AI to plan your whole day?: → Reclaim.ai.