calsyncBusy only, per calendar
Copies can say just Busy, with no title or location. Private events always do.
MITFree, open source, runs on your machine
Every calendar.Always in sync.
A meeting on your work calendar shows up on your personal one, and the other way round. Google, Microsoft 365 and any .ics feed. Nothing hosted, nothing to pay.
Works withGoogle CalendarMicrosoft 365Outlook.comAny .ics feed
Why calsync
A meeting on one calendar is a double-booking on the other.
Without calsyncThursday
Personal
Dentist10:00
Work
Client call10:00
A colleague booked over the dentist. They couldn't see it.
With calsyncThursday
Personal
Dentist10:00
Client call11:00 · copy
Work
Busy10:00 · copy
Client call11:00
Work saw Busy at 10:00 and picked 11:00 instead.
Two-way sync
One schedule. However many calendars.
Each writable calendar gets one tagged copy of every real event from the others. Move the meeting once and every copy follows. A published .ics link can join in too, one way.
Safety
It only touches what it made. Nothing else.
Stops before a big delete
Nothing large disappears until you've looked. A calendar that won't load is left alone.
Only its own copies
calsync edits and deletes only events it created. Yours are never touched.
No double invites
A meeting already there through a shared invite isn't copied again.
One-button undo
One button, or calsync purge, removes every copy it made.
How it works
Connect. Preview. Then it runs itself.
Connect
Add each calendar on one page. Google and Microsoft each need a free sign-in app of your own, about 10 minutes each.
Preview
See what would be added, updated and removed on each calendar. Nothing changes until you start it.
Sync
Press Sync now. After that it runs in the background, every 5 minutes unless you pick another interval.
Private
Your calendars. On your own machine.
0accounts to make
0databases to run
1process or container
$0MIT licensed
- Your sign-ins
- Files on the machine that runs calsync
- Who can reach it
- This machine, until you change that
- Who it talks to
- Your calendars, and nothing else
- Before the internet
- Put it behind your own HTTPS proxy
Compare
Same sync. No subscription.
ToolPer yearTwo-wayBusy onlyYour sign-ins
calsync$0YesPer calendarStay on your machine
OneCal$60YesYesOn their servers
Reclaim.ai$96YesHides detailsOn their servers
CalendarBridgeabout $48YesYesOn their servers
Cheapest paid plan for one person, at list prices seen on 3 November 2026.
Before you start
What to know first.
- Needs a free sign-in app of your own.
- Microsoft
- Needs one too. Some school and work tenants block outside apps. A published .ics link still works, one way.
- Window
- The next 120 days. Repeating events are copied as single occurrences.
- Hosted version
- There isn't one. The machine running calsync needs to be on.
Install
Pick one. Both take a minute.
With Docker
git clone https://github.com/jakescalesAI/calsync
cd calsync
docker compose up -d
docker compose logs calsyncOpen http://localhost:8484. The first visit asks for the setup code from those logs. Then you choose a password.
With Python 3.10 or newer
pipx install git+https://github.com/jakescalesAI/calsync
calsync webThe same page opens at http://localhost:8484.