Gobo

Private calendar blocking for the Mac

Your colleagues book meetings by what your work calendar shows; your dentist and your kid's recital live on calendars it can't see. Gobo mirrors them onto it as plain Busy blocks. No titles, no details. Just the time.

Download on the Mac App Store

One-time purchase
No subscription, no account
No IT approval
macOS 14 or later

Try it here

Flip a switch and watch your work calendar.

On the left, a Tuesday on a personal calendar. On the right, the same day on a work calendar, as a colleague sees it. Mark something Free and its block disappears; mark it Busy and it comes back.

PersonaliCloud · Tuesday

20‑minute travel buffers Mirror title

WorkExchange · what colleagues see

Work meeting Gobo block Travel buffer

Buffers follow the default rule: only events with a location get them, so the phone call doesn't. In the app the change lands on the next sync, which runs as soon as you flip the switch.

Why it exists

Built inside the problem

My personal life is in iCloud. My work calendar lives in a university tenant I don't administer, and the IT department that runs it (reasonably) refuses third-party OAuth grants. Every calendar sync service fails at exactly that wall, because every one of them needs permission from the work side.

Gobo doesn't ask. It runs entirely on your Mac, through the same built-in calendar access Apple's own Calendar app uses; if your work calendar is on your Mac, Gobo can protect your time. Five minutes to set up. No ticket, and nothing for an administrator to block.

How it works

Set it up once. Then it gets out of the way.

Choose your calendars. Personal / Medical / Family, whatever holds your life, and one work calendar to protect it on. Setup walks you through it and shows you every block it would create before it writes anything.

Gobo mirrors the time, never the event. Each commitment becomes an anonymous busy block, with travel buffers baked in if you want them. Colleagues see that you're unavailable; they never see why.

Mark anything flexible as Free. Events marked Free are skipped. That one flag is the whole system; no naming conventions, no second calendar to maintain.

After that, Gobo lives in the menu bar. It syncs every 15 minutes, again whenever your calendars change, and does a full pass overnight. Move a dentist appointment and its block moves with it; cancel it and the block goes away.

What reaches your work calendar

The start and end time
A title you choose (“Busy” by default)
Availability set to Busy
A note reading “This busy block is managed by Gobo,” with an anonymous code so Gobo can find its own blocks

What stays on your Mac

The event title
Location
Notes and links
Attendees
Which calendar it came from
Alerts

A look inside

Everything is one menu bar icon away.

Gobo is a small menu bar app with a single settings window. Here are the parts you'll actually use.

Gobo's Availability tab: upcoming personal events, each with a Busy/Free switch

The switch

The Busy/Free switch Apple took away

Apple's Calendar app no longer lets you mark an iCloud event Free or Busy on the Mac. Gobo gives the switch back: flip any upcoming event from inside the app, and its busy block appears or disappears on the spot.

The flag is written to the event itself, so it stays with the event wherever that calendar syncs. For a repeating event, the switch changes only that occurrence; next week's piano lesson is still Busy. Exchange events keep their own “Show As” control in Calendar, and Gobo respects that too.

Reference

Every setting, explained.

The defaults are what most people want. Here is everything you can change, and what it does.

Rules

A rule takes events from one or more source calendars and blocks time on one target. You can have as many rules as you like, each with its own filters and buffers.

Setting	What it does	Default
Sources	The calendars whose events should block time.	Chosen in setup
Target	The calendar the blocks go on, usually the one colleagues check. Read-only and subscribed calendars aren't offered, because Gobo can't write to them.	Chosen in setup
Mirror title	What each block is called on the work side.	Busy
Days back / ahead	How far around today Gobo looks: up to 30 days back and 365 ahead.	1 / 90

Filters

What doesn't get mirrored.

Setting	What it does	Default
Skip events marked Free	The main switch. Anything non-committal, marked Free on its own calendar, stays off your work calendar.	On
Skip all-day events	Birthdays and holidays don't block your whole day.	On
Skip tentative events	Leaves out events marked tentative.	Off
Minimum duration	Ignores anything shorter than this, from 5 to 240 minutes.	Off
Exclude titles containing	Comma-separated words; any event whose title contains one is left out. Useful for calendars that have no Busy/Free flag.	None

Travel buffers

Time to get there and back, folded into the block.

Setting	What it does	Default
Before / after	Extends each block, up to 120 minutes either side, in 5-minute steps.	20 / 20 min
Only events with a location	A phone call doesn't need travel time; a clinic visit does.	On

Syncing

Setting	What it does	Default
Sync every	5, 15, 30, or 60 minutes. Gobo also syncs whenever your calendars change, and does a full pass nightly.	15 min
Launch at login	Starts Gobo quietly in the menu bar.	Your choice
Pause	From the menu bar, for an hour or until tomorrow.
Sync Now	From the menu bar, whenever you want it.

Keeping track

Setting	What it does	Default
Menu bar status	Last sync, next sync, and how many blocks Gobo is managing.
Preview	Every block a rule would create, update, or remove, with the source titles shown to you alone. Nothing is written from this screen.
Activity	A timestamped log of every change Gobo writes. The log never leaves your Mac.
Remove All Mirrors	In the Danger Zone. Deletes every block Gobo has made, and nothing else.

Privacy

Private by architecture, not by policy

No network code. At all.

No servers, no account, no analytics, no update pings. Gobo works with the network cable unplugged, and its sandbox isn't permitted to open a connection in the first place.

Read it yourself

The sync engine is open source (MPL‑2.0). Read it, confirm there is no network call in it, and then decide whether to trust the packaging.

One permission

Calendar access, and nothing else. macOS asks once, and you can revoke it in System Settings at any time. Why it has to be full access is answered below.

Preview before it writes

See every block Gobo would create, update, or remove before it touches your work calendar.

Conservative on purpose

One-way mirroring only. Gobo never edits or deletes an event it didn't create, including ones you titled “Busy” yourself, and removes all of its own blocks with one click. The one exception is the Busy/Free switch, which changes only that flag, and only when you flip it.

Careful when things go missing

If a source calendar disappears, say an account signs out, Gobo holds off on deleting rather than wiping your blocks.

What's open, and what isn't

The engine is public at github.com/mfbergmann/gobo-core: the sync logic, the layer that reads and writes your calendars, and a command-line tool. Its v1.0 tag matches the App Store build. The menu bar app around it (settings, scheduling, Preview, and Activity) is not open source.

The closed part can still be checked. Once Gobo is installed, this Terminal command lists what macOS allows it to do:

codesign -d --entitlements - /Applications/Gobo.app

You'll see the app sandbox and calendar access, and no network.client entitlement, which is the one an app needs to make an outgoing connection.

The App Store privacy label reads “Data Not Collected.” The details are in the privacy policy.

What you get

One purchase, that's it.

Every feature, with no tiers
Free updates
No subscription
No account to make
Works offline
Open-source sync engine

Priced in your own currency on the Mac App Store. There's no free trial, because a trial would need a server; the demo above, the Preview screen, and the App Store's refund policy are there instead.

Why “Gobo”?

A gobo is the cut metal template a lighting designer puts in front of a stage light; the shape of the beam is decided by what you deliberately mask out. The word is probably a contraction of go-between, the thing that stands between the light and the scene.

Both meanings apply. Gobo masks your events, and it stands between your personal life and your work calendar. Only the shape of your time passes through.

Questions

Do I need my employer's permission?

No. Gobo never talks to your employer's systems; it works through the calendar accounts already on your Mac, the same way the built-in Calendar app does.

Which calendars does it work with?

Anything that shows up in Calendar on your Mac: iCloud, Google, Exchange, and other CalDAV accounts all live in the same local calendar store, and Gobo reads from and writes to that store. The target has to be a calendar you can edit. If your work calendar is Microsoft 365, read the next answer first.

My work calendar is Outlook / Microsoft 365. Will Gobo work?

Probably, for now. Check before you buy; it takes a minute.

Gobo writes to your work calendar through the Microsoft account in your Mac's Calendar app. Calendar on the Mac reaches Microsoft 365 through an older connection called Exchange Web Services (EWS). Microsoft began switching EWS off on 1 October 2026; each organisation's IT can keep it on until 1 April 2027, when it goes away for everyone. Apple says a future macOS 27 update will move Calendar to Microsoft's newer connection, and hasn't said when.

If your organisation still has EWS on, everything works. If it doesn't, your Mac's Calendar stops syncing that account: Gobo would still make its blocks, but they'd stay on your Mac and colleagues wouldn't see them. Nothing in Gobo needs to change; once Apple's update arrives, the blocks sync like any other event.

The check: in Calendar on your Mac, make a test event on your work calendar, then look for it in Outlook on the web. If it shows up, Gobo will work. If it doesn't, or Calendar shows a warning next to the account, hold off for now, or ask your IT department whether EWS is still enabled. Microsoft is switching organisations over in stages, so a check that passes today can fail later; if colleagues start booking over your blocks, run it again.

Exchange servers your organisation runs itself aren't affected, and neither are Google, iCloud, or other CalDAV calendars. Last checked 13 October 2026.

What do colleagues actually see?

Colleagues who see only free/busy see you as busy. Anyone with full view of your work calendar, such as an assistant or delegate, sees a block titled “Busy” (or any title you choose) and a note saying Gobo manages it. Nothing from the source event crosses over.

Why does it need full calendar access?

macOS offers two levels: full access, or write-only. There is no way to grant access to particular calendars. Gobo has to read your personal events to mirror them, so write-only won't do. You can switch access off at any time in System Settings → Privacy & Security → Calendars.

Some of my calendars don't have a Busy/Free setting.

Not every calendar type carries the flag. Gobo tells you when you pick one as a source; every event from it will be mirrored, so use keyword exclusion or a minimum duration to filter it instead.

Does my Mac need to be on?

For new changes to cross over, yes. Gobo does its work on your Mac, so an appointment you add on your phone gets its block the next time your Mac is awake and syncing. Blocks Gobo has already written stay on your work calendar like any other event, whether your Mac is on or not.

How does it handle repeating events?

Each occurrence gets its own block, and each one follows its source: if a single occurrence moves, only that block moves. Flipping one occurrence to Free in Availability leaves the rest of the series alone.

Can I have more than one rule?

Yes. Personal and Family onto your work calendar, Medical onto a second one, each with its own filters and buffers. Rules can be switched off without being deleted.

How do I undo it, or uninstall?

Switch your rules off, then use Remove All Mirrors in the Danger Zone. It deletes every block Gobo has made, and only those. After that, quit and delete the app as usual. If you just need a break, pause syncing from the menu bar.

What data does Gobo collect?

None. The App Store privacy label reads “Data Not Collected,” and the open-source engine makes that checkable rather than a promise. See the privacy policy.

What does it cost?

A one-time purchase on the Mac App Store, in your own currency. No subscription, no tiers, and no free trial, because a trial would need a server.

Which version of macOS do I need?

macOS 14 Sonoma or later.

Gobo is made by one person (with their AI collaborator), on the machine it runs on. If your work calendar has been eating your life, I'd like to hear how this goes: gobo@bergmann.ai.

Still deciding? Ask an assistant.

These open a chat with this page and the engine's source code already in the question. You shouldn't have to take my word for it.

Ask ChatGPT Ask Claude Ask Perplexity

Your dentist doesn't need to be on your work calendar. The time does.

Five minutes to set up, and nothing for IT to approve.

Download on the Mac App Store

One-time purchase
No account
macOS 14 or later