Keeper.sh is the SyncThemCalendars alternative when you want a free plan, when one of your calendars is on Fastmail or another CalDAV server, or when you run more than the 5 calendar syncs in SyncThemCalendars' entry plan. SyncThemCalendars (checked 10 November 2026) syncs Google Calendar, Outlook and iCloud, starts with a 14-day trial and has three paid plans covering 5, 16 and 36 calendar syncs.
Keeper.sh is a calendar sync service that copies events between Google Calendar, Outlook, iCloud, Fastmail and any CalDAV server, so every calendar shows you as busy at the same times. It is free for 2 calendar accounts and 3 connections, and Pro is $5 a month for unlimited calendars.
Keeper.sh and SyncThemCalendars side by side
The table lists what each service charges, which calendars it connects, how fast changes arrive and what a copy shows, with each SyncThemCalendars figure linked to its source (checked 10 November 2026).
| Keeper.sh | SyncThemCalendars | |
|---|---|---|
| Free plan | 2 calendar accounts, 3 connections, no card (pricing) | None: a paid plan is needed after the trial (SyncThemCalendars) |
| Entry price | $5/month, or $45/year, for unlimited calendars | Basic: $4.99/month billed monthly, or $3.99/month billed yearly ($47.88/year), for 5 calendar syncs (SyncThemCalendars) |
| Calendars supported | Google Calendar, Outlook, iCloud, Fastmail, any CalDAV server; .ics links read-only | Google Calendar, Outlook and Office 365, iCloud (SyncThemCalendars) |
| Update speed, Google and Outlook | Within seconds on Pro; every 30 minutes on Free | "in moments"; no figure published (two-way calendar sync) |
| Update speed, iCloud and CalDAV | Every minute on Pro; every 30 minutes on Free | iCloud is checked "every few minutes" (Apple iCloud calendar sync) |
| What a copy shows by default | A busy block named after the source calendar; title, description and location hidden | Not published; title, description and location can each be hidden behind a "Busy" block |
| Trial | None needed: the Free plan has no time limit | 14 days, no card (SyncThemCalendars) |
What does each one cost?
SyncThemCalendars prices by the number of calendar syncs. Billed monthly, Basic is $4.99 a month for 5, Premium is $9.99 for 16 and Professional is $19.99 for 36. Billed yearly, they are $3.99, $7.99 and $17.99 a month, which is $47.88, $95.88 and $215.88 a year. Each plan covers 1 user with unlimited calendars and events. All plans include a 14-day free trial with no card, and a paid subscription is needed afterwards (SyncThemCalendars).
On Keeper.sh, Free covers 2 calendar accounts and 3 connections. Pro is $5 a month or $45 a year for unlimited calendars, priced per person, not by sync (pricing). A Keeper.sh account is one signed-in calendar service, however many calendars it holds, and Pro has no limit on connections, no seats and no higher tier, so the price is the same at 6 connections as at 36. Sign-up needs no card: create a Keeper.sh account.
Which calendars does each one connect?
SyncThemCalendars connects Google Calendar, Microsoft Outlook and Office 365, and Apple Calendar on iCloud, in any combination (SyncThemCalendars).
Keeper.sh connects Google Calendar, Outlook, iCloud, Fastmail and any CalDAV server, and reads and writes all five. Fastmail connects with an app password, and Nextcloud or another CalDAV server connects with its address and sign-in details. Keeper.sh also takes an .ics link as a read-only source, so a timetable or a shared schedule can block your time too.
How fast does a change reach the other calendar?
On Pro, Google and Outlook changes land within seconds, and iCloud, Fastmail and CalDAV changes land every minute. On Free, changes land every 30 minutes.
SyncThemCalendars says "Google and Outlook notify us the moment something changes, so copies update in moments" (two-way calendar sync) and that it checks an iCloud calendar "every few minutes" (Apple iCloud calendar sync).
How does two-way sync work in each?
On Keeper.sh, each connection runs one way, so two-way sync is two connections. A two-way pair uses 2 accounts and 2 connections, which fits the Free plan with one connection spare.
SyncThemCalendars sets direction when a sync is created: "Choose two-way when creating a sync and both calendars become mirrors" (two-way calendar sync).
What does a copied event show?
Keeper.sh hides event details unless you turn them on. Each copy is a busy block named after the source calendar. The title, description and location are hidden by default, Pro can turn them back on per calendar, and guest lists are never copied. The calendar sync features page lists the other settings a connection has.
SyncThemCalendars lets you "hide title, description and location behind a 'Busy' block", field by field (two-way calendar sync).
How does Keeper.sh handle calendar data?
Keeper.sh encrypts your data at rest and in transit, is operated from Alberta, Canada under Canadian privacy law including PIPEDA, and deletes the data tied to your account within 30 days of you deleting it, except where the law or a legitimate business purpose such as fraud prevention requires it to be kept. The privacy policy has the details.
Can an assistant work with your calendars?
Keeper.sh has a REST API and an MCP server at https://www.keeper.sh/mcp. The MCP server gives an assistant such as Claude 27 tools to list calendars, read events, create, update and delete them, answer invitations and find free time. It signs in through OAuth 2.1 with a consent screen and needs no API key. On Free, the two share 25 calls a day, and Pro has no daily cap. The Keeper.sh MCP server documentation lists every tool.
What SyncThemCalendars offers
- Entry price: Basic is $4.99 a month billed monthly, or $3.99 a month billed yearly, for 5 calendar syncs, which suits someone with a small, fixed set of Google, Outlook or iCloud calendars.
- Two-way sync as one choice: a single sync can copy in both directions.
- Per-field privacy: the title, description and location of a copy are hidden or shown one by one.
When Keeper.sh fits
- Free plan: you have two calendar accounts and want them synced without a subscription.
- Fastmail or CalDAV: one of your calendars is on Fastmail, Nextcloud or another CalDAV server.
- Many connections: you run more than 5 calendar syncs, and want one price that does not depend on the count.
- Shareable calendar link: you want one shareable calendar link covering the calendars you choose, which any calendar app can subscribe to. Its events read "Busy" by default.
Step-by-step setup is in how to sync iCloud and Google Calendar and how to sync iCloud Calendar with Outlook.
Common questions about Keeper.sh and SyncThemCalendars
Is there a free alternative to SyncThemCalendars?
Yes. Keeper.sh syncs 2 calendar accounts over 3 connections on its Free plan, with changes landing every 30 minutes and no card required. SyncThemCalendars offers a 14-day trial and paid plans from $4.99 a month billed monthly, or $3.99 a month billed yearly.
Does Keeper.sh limit the number of syncs?
Only on the Free plan. Keeper.sh Pro has no limit on accounts or connections. SyncThemCalendars' three plans cover 5, 16 and 36 calendar syncs.
Can Keeper.sh sync Fastmail or Nextcloud calendars?
Yes. Keeper.sh connects Fastmail with an app password and Nextcloud as a CalDAV server, and it can read from and write to both.
How fast does Keeper.sh update compared with SyncThemCalendars?
On Keeper.sh Pro, Google and Outlook changes land within seconds, and iCloud, Fastmail and CalDAV changes land every minute. On Free, changes land every 30 minutes. SyncThemCalendars says Google and Outlook copies update in moments and iCloud is checked every few minutes.
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