XCalSync vs Calensync vs OGCS: Picking a Calendar Sync Tool (2026)

Posted: May 8, 2026

Search for “calendar sync” between Google and Outlook and you’ll find three tools repeatedly: XCalSync, Calensync, and OGCS (Outlook Google Calendar Sync). They solve roughly the same problem but in very different shapes — and the right one for you depends on whether you want a free local tool, a simple hosted sync, or fine-grained control over what gets copied.

This is a practical comparison of how each is hosted, what they sync, and which fits which use case.

Quick comparison

For specifics on pricing and feature changes since this was written, check each tool’s site directly — SaaS plans change.

How each one is shaped

OGCS (Outlook Google Calendar Sync)

OGCS is the oldest and most established option in this space — a free, open-source Windows desktop app maintained on GitHub. You install it on your machine, configure your sync direction and filters, and run it on a schedule (or manually). The actual sync happens locally; nothing is hosted on a third-party server.

Strengths:

• Free with no licensing constraints.
• Open source — you can read exactly what it does with your data.
• No third-party data hosting; everything runs on your machine.
• Mature; many years of edge cases ironed out.

Tradeoffs:

• Windows-only. No Mac, Linux, or mobile.
• Only syncs while your machine is on. Close your laptop, miss a sync.
• Setup involves OAuth tokens and configuration files; non-technical users can struggle.
• Maintenance is volunteer-driven; release cadence varies.
• UI is functional rather than polished.

Best for: developers and power users on Windows who want a free, transparent tool and don’t mind running it locally.

Calensync

Calensync is a more recent hosted SaaS, oriented toward simple Google ↔ Outlook sync without much configuration. You sign in with both calendar providers, set the sync direction, and the service handles the rest.

Strengths:

• Browser-based — works on any OS.
• Hosted; syncs run regardless of whether your machine is on.
• Simpler setup than OGCS.

Tradeoffs:

• Closed source; you trust the provider with calendar data.
• Fewer event-level controls than XCalSync (no buffer time, limited filtering).
• Pricing varies — check the site for current plans.

Best for: users who want a hosted, set-it-and-forget-it sync between two calendars and don’t need fine-grained controls.

XCalSync

XCalSync (this site) is a hosted SaaS focused on giving you finer control over what gets synced and how it appears in the destination.

Strengths:

• Hosted; runs 24/7 regardless of your machine state.
• Browser-based — any OS.
• Event filters: only sync weekdays, only events matching a name pattern, only events with specific attendees, skip “tentative” or “free” status events.
• Title rewriting: replace personal event titles with “Busy” in the work calendar so colleagues see availability without reading details.
• Buffer time: add a configurable buffer before or after copied events.
• Supports multiple SyncPairs on higher tiers (one Google + multiple Outlook accounts, for example).
• Free tier includes one SyncPair, configurable as one-way or two-way.

Tradeoffs:

• Closed source.
• Hosted SaaS — you’re trusting a third-party provider with calendar access (via OAuth scopes).
• Paid plans for more than one SyncPair (starting at $4/month).

Best for: people who need a hosted sync that does more than just mirror events — anyone who wants to filter what copies, anonymize event titles in the destination, or sync more than two calendars.

Picking the right tool

The decision usually comes down to three questions.

1. Are you on Windows and OK with a desktop app that only runs when your machine is on?

If yes, OGCS is hard to beat for free, open-source basic sync. If your machine is rarely off (e.g., a desktop PC always plugged in), the always-on requirement is fine.

If you’re on Mac, Linux, or want sync to keep running while your laptop is closed, OGCS is out.

2. Do you need event-level controls (filters, anonymization, buffer time)?

If yes, XCalSync is the only one of the three that exposes these as standard features. The use case is anyone whose two calendars contain content that shouldn’t appear verbatim in the other — a personal calendar mirrored into a work calendar where colleagues will see it, for instance.

If you’re fine with everything being mirrored as-is, Calensync or OGCS work.

3. How many calendars do you need to keep in step?

For two calendars (one Google + one Outlook), all three options work.

For more — multiple Google accounts, multiple Outlook accounts, or a mix — XCalSync’s multi-SyncPair model handles it on paid tiers. OGCS supports multiple profiles but only runs them serially, which can lag on machines that aren’t always on. Calensync supports paired calendars on higher plans.

Common questions

Are these tools secure?

All three tools that use OAuth (XCalSync, Calensync, OGCS via your local credentials) request the minimum scopes needed to read and write calendar events. None require mailbox access. Hosted services (XCalSync, Calensync) store OAuth tokens to keep syncs running; OGCS stores them locally on your machine.

For sensitive calendars, the question is which trust model fits — local (OGCS) keeps tokens on your device but requires the device to be on; hosted (XCalSync, Calensync) keeps tokens on the provider’s servers but runs 24/7. Neither is universally better.

Will any of them break my calendar?

The risks are duplicates (most often from running multiple one-way syncs in opposite directions instead of one two-way SyncPair) and deletion propagation (a delete in one calendar replicates to the other). All three tools document these risks. For peace of mind on first setup, sync into a dedicated destination calendar so a misconfigured run can be undone by deleting that one calendar.

Can I migrate from OGCS to a hosted tool?

Yes. The destination calendar’s events from OGCS will be picked up as native events by the new tool, which then continues to sync them. The catch is that internal event IDs differ between tools, so on first run the new tool may treat the existing OGCS-synced events as fresh events to be matched up. Test on a non-critical calendar first.

What about other tools (Zapier, IFTTT, native Microsoft 365 connectors)?

Zapier and IFTTT can do basic event mirroring but don’t handle two-way sync, recurring event edge cases, or attendee mirroring well — they’re built for trigger-action flows, not state mirroring. Native Microsoft 365 connectors are restricted to within-Microsoft sync (no Google support). For the specific Google ↔ Outlook two-way use case, the three tools in this comparison are the practical options.

Verdict

If you want free and open source on Windows, OGCS is the answer.

If you want simple hosted sync with no configuration, Calensync is the lighter option.

If you want filtering, anonymization, buffer time, or multiple SyncPairs — and a hosted service that runs 24/7 — XCalSync covers more ground.

XCalSync’s free tier covers a single SyncPair (configurable as two-way) with no credit card required. The fastest way to know if it fits your workflow is to set it up against a non-critical pair of calendars and watch the first sync.

Get started for free.