Tool comparison
Kalender Sync vs. MergeCal – feed merger or real sync?
MergeCal and Kalender Sync often get mentioned in the same breath – yet they solve different problems. MergeCal is a feed merger: it bundles many iCal calendars into a single subscription link. Kalender Sync is a sync service: it writes real events into your calendars, in both directions. Both have their place – here's an honest look at when each tool is the right one.
Background
What can MergeCal do?
MergeCal is an open-source project (AGPL-3.0, Django/Python) by the US company MergeCal, Inc. that combines any number of iCal/ICS feeds into a single merged feed. Sources can be Google, Apple, Outlook, but also Meetup, Discord, Twitch or booking platforms like Viator and GetYourGuide. You then subscribe to the combined feed in your calendar app or drop it into listing sites – a popular use case is showing vacation-rental availability across multiple portals. Pricing: Personal at $2/month (3 calendars, hourly updates), Supporter at $10/month (10 calendars), Business at $20/month (unlimited), each with a 14-day trial without a credit card. The project is actively maintained and has its own community.
Strengths
Where MergeCal is strong
One subscription link instead of ten
If you just want to view many calendars – club dates, community events, occupancy schedules – a single combined feed is exactly the right abstraction. Subscribe once, and every source shows up in one view. For that job, MergeCal is a clean tool.
Exotic feed sources
Meetup, Discord events, Twitch stream schedules, Viator and GetYourGuide bookings: MergeCal accepts any iCal feed, which makes it especially attractive for vacation-rental hosts and community organisers – a niche classic sync tools don't serve at all.
Open source with an affordable entry
The code is open on GitHub under AGPL-3.0, the project is actively developed, and at $2/month the Personal plan is a very affordable entry point. A likeable, transparently built product.
Where Kalender Sync wins
Where Kalender Sync wins
Real events instead of a read-only feed
The fundamental difference: MergeCal delivers an ICS subscription – your calendar merely displays the events. Kalender Sync writes real events into the target calendar via API. That difference becomes practical the moment availability matters: subscribed feeds are often ignored by booking tools and colleagues doing free/busy lookups – real events block reliably.
Freshness that doesn't depend on your calendar app
How often an ICS subscription refreshes is up to the calendar app – Google Calendar, for instance, refreshes external feeds on its own schedule, sometimes only after hours. Kalender Sync actively writes changes into the target calendar in real time, regardless of when the app would next poll a feed.
Two-way sync instead of a one-way street
A merged feed is by definition a one-way street: you can't edit the events at the destination, and nothing flows back. Kalender Sync synchronises bidirectionally – changes in any connected calendar land everywhere.
Three visibility levels per sync
With Kalender Sync you decide per synchronisation what arrives: "busy only", "title + time" or "full details" – with custom display names for blocked slots. A feed merger passes events through; fine-grained data minimisation per recipient is a sync feature.
Live-sharing into other calendars
Kalender Sync embeds your availability directly into another person's calendar by invitation – as real events, without them having to subscribe to or maintain a feed. They accept once, and from then on everything stays in sync automatically.
A German privacy stack with a DPA
Kalender Sync is run by PPJ Venture Labs UG in Munich, GDPR- and BDSG-compliant, hosted at Hetzner in Nuremberg, with a DPA for business customers. MergeCal is a US Inc.; its privacy policy contains no statements on GDPR, EU hosting or a DPA that we could find. For law firms, schools and companies, that's a deal-breaker.
9 provider types and a permanently free plan
Kalender Sync connects Google, Microsoft Outlook/M365, Apple iCloud, GMX, WEB.DE, mailbox.org, Infomaniak kSuite, CalDAV and iCal feeds via API – as the only tool in this comparison with the German providers GMX and WEB.DE. One synchronisation is permanently free, then Basic from €4/month and Business at €10/month – whereas MergeCal's trial ends after 14 days.
Decision guide
When should you pick which?
MergeCal is the right choice if:
- You just want to view many calendars in one place – with no channel back.
- You want to bundle feeds from Meetup, Discord, Twitch or booking platforms.
- You're a rental host and need occupancy from several portals in one feed.
- A read-only ICS subscription with hourly updates is enough for you.
Kalender Sync is the right choice if:
- Your events should block as real entries – not just show up as a subscribed overlay.
- You need two-way sync: changes flow in both directions.
- You want to share your availability live into other people's calendars – with selectable visibility per sync.
- You need a German contractual partner with a DPA, GDPR/BDSG compliance and Hetzner hosting.
- You want the broadest provider coverage in this comparison: 9 provider types – Google, Microsoft Outlook/M365, Apple iCloud, GMX, WEB.DE, mailbox.org, Infomaniak kSuite, CalDAV and iCal feeds. Kalender Sync is the only tool in this comparison with the German providers GMX & WEB.DE.
Ready for real events instead of read-only feeds?
Connect your calendars in a few clicks – GDPR-compliant, hosted in Germany, with two-way sync and genuine live-sharing.
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