Last updated 5 August 2026
Your mail travels between Google and this Mac, and nowhere else — unless you switch on the AI features, which is the one exception and has a section of its own below. Nothing about you or how you use Kirby is sent to me either way.
Kirby can put your mail in the Mac's search index so ⌘Space finds it. This is off unless you switch it on in Settings › Privacy, and it is the one setting that moves anything out of Kirby's own custody.
Spotlight's index belongs to macOS rather than to Kirby, which means other software on this Mac can search what's in it. That is the trade, and it's the reason the setting exists instead of this being on by default.
Only the sender, the subject and the preview line are added. Message bodies never are. Turning the setting off deletes everything Kirby put there rather than merely stopping it adding more, and the example mailbox is never indexed at all.
Your mail is kept in a database inside Kirby's own folder on this Mac. That's what makes the app fast and what makes it work offline. It is not encrypted separately from the rest of your disk — if you use FileVault, which you should, it's encrypted along with everything else.
The token that lets Kirby talk to Gmail on your behalf is kept in the macOS Keychain, not in the database and not in a file.
Deleting Kirby's container, or disconnecting an account in Settings, removes what it holds. Disconnecting also revokes nothing at Google's end — you can withdraw Kirby's access entirely at myaccount.google.com/permissions.
To Google: requests for your mail, and the messages you send. That's the whole list.
To me: nothing, unless you turn on the AI features — see below, because that is the one exception and it deserves its own section. There is no analytics, no telemetry, no crash reporting service, and no licence check that phones home with your address. I do not know how many messages you have, who you write to, or whether you use the app at all.
To anyone else: nothing, with one exception you control. Messages that contain images hosted elsewhere are blocked until you choose to load them. Loading them tells that server you opened the message — which is exactly why senders use them, and exactly why Kirby doesn't do it without being asked.
Kirby's use of information received from Google APIs follows the Google API Services User Data Policy, including the Limited Use requirements.
Your Gmail data is used only to provide the features you can see in the app: reading, searching, organising, and sending your mail. It is never used for advertising, never sold, never transferred to anyone, and never read by a human. No machine-learning model is trained on it.
Kirby writes a note about what it was doing when it stopped, into its own folder on this Mac, and shows it to you the next time you open the app. It contains the version, your macOS version, and the addresses the code was executing. It contains no mail, no addresses of anyone, and nothing that identifies you.
It goes nowhere unless you press the button, which opens your own mail app with the text already in it so you can read every word before it's sent. It is deleted after you've been shown it, whether you send it or not.
Kirby can summarise a conversation, answer a question about one, or draft a reply. This is the one part of the app that sends your mail somewhere, and it is off until you turn it on.
When it is on, the message you use it on is sent to Anthropic, the company that makes Claude, by way of a small server of mine that holds the key. That server keeps one number: how many free requests an installation has used. It does not store your mail, your address, or what you asked.
Anthropic does not use it to train their models. They keep it briefly to watch for abuse of their service, then delete it. I am describing somebody else's policy here rather than my own, so check theirs if it matters to you.
Messages you never use AI on are never sent anywhere. Turn the feature off in Settings and nothing leaves this Mac except to Google, exactly as before.
If you turn on sender photos, Kirby reads your address book to find a picture for the person who wrote to you. It reads it only; it never changes a contact, and it never sends any part of your address book anywhere.
Most mail clients get these photos from Gravatar or from the sender's website, both of which mean telling a third party who you correspond with. Kirby doesn't do that, which is why people who aren't in your address book get their initials instead.
If you buy Kirby's premium features, the purchase is handled by Apple. I never see your card details, your address, or your name — only that a purchase happened.
Kirby isn't aimed at children and collects nothing from anyone, of any age.
If this policy ever changes in substance, the app will say so rather than quietly updating a page nobody reads. The date at the top is the last time anything here changed.
Write to privacy@kirbymail.app and I'll answer it myself, because there is nobody else here to answer it.