Participant mail never leaves your machine.
Klar filters spam inside Apple Mail, on your own Mac. The extension that reads your inbox has no network permission, so classification adds nothing to the list of people who have seen your data.
A filter is a recipient, and recipients go on the record.
Research correspondence is participant data as soon as it names one. Consent forms, withdrawal requests, symptom diaries and scheduling threads all arrive by mail, and article 89 lets you keep processing them for research only if the safeguards are real ones.
The safeguard that gets skipped is the mail filter. A cloud filter reads the message to score it, which makes its operator a recipient of participant data: a line in the record of processing, a transfer to justify, and a contract to hold. Nothing about it is research-specific, which is exactly why it goes unlisted.
GDPR art. 89: safeguards for processing for scientific research purposesNo recipient, because nothing is sent.
Klar is a Mail extension. It scores each message on your Mac as it arrives, without uploading it. The part that reads your inbox ships without macOS network permission, and one codesign command shows that from the installed app rather than from a promise. There is no operator to add to the record, no transfer to justify, and no contract to hold, because there is no second party.
The part of Klar that reads your mail is an Apple-sandboxed Mail extension shipped without the network entitlement. It is not that we promise not to send your mail anywhere. It is that macOS refuses the connection, because the permission was never requested. Classification happens on your Mac, instantly.
What that means in practice
- No network access
- The free App Store app and its Mail extension ship without the network entitlement. macOS refuses any connection they try to open. This is a permission the app does not hold, not a policy it promises to follow.
- The model ships with the app
- The classifier is a multilingual transformer inside the app bundle. Nothing is fetched when a message arrives, so it works the same on a train as it does in the office.
- No account
- There is nothing to sign up for and no licence server the free app calls. Unless you contact us or choose to send an Email report, we do not know who you are.
- The engine is open source
- The scoring engine is AGPLv3. Your IT people do not have to take our word for any of this. They can read it, build it, and watch what it does.
Questions your compliance officer will ask
Do we need to add Klar to our record of processing?
Not for classification, and the reason is structural rather than contractual. A processor is a party that processes on your behalf; Klar's classification happens inside your own machine's memory and produces no transmission, so there is no party. What does leave is the Email report, and only when a user composes and sends it themselves: it is an editable draft in their own mail app that attaches the message they selected, so it is a disclosure they make deliberately, message and all. Nothing goes automatically.
Our institution already filters mail at the gateway. Does this add anything?
It changes what the second filter costs you. Most desks end up running one anyway, because a gateway tuned for the whole institution is not tuned for a study's correspondence, and the usual second filter is a cloud service with its own operator to list. Klar is the second filter that adds no one. If you also want the first one to stay in-house, Klar Pro runs the same engine as a milter on your own mail server.
Does filtering send anything off the machine?
No. The free App Store app and its Mail extension have no network permission. If you choose Email report, Klar opens an editable draft in your own mail app; nothing leaves until you send it. Do not include confidential correspondence unless you are authorised to share it. Klar Plus, the paid companion you install yourself, separately uses the network for its licence, model and version checks. None carries your mail. The full list is on the local-first page.
Do we need a data processing agreement with you?
That is a question for your own counsel, and it depends on which part of Klar you run. Routine filtering sends us nothing. A user who sends an Email report may share selected messages, diagnostics and a removable monthly usage summary; our privacy policy explains what we then hold. Decide whether staff may use that report action with confidential correspondence.
What we are not claiming.
We are not offering legal advice, and a spam filter does not make anyone compliant. Your obligations are yours, and your bar, your regulator or your DPO is the right place to test them. What we can tell you is exactly where the software runs and what it is permitted to do, which is the part most vendors leave you to infer.
We are also not claiming perfect filtering. No filter is, and any vendor quoting you a single accuracy number is quoting a number from their corpus, not your inbox. What we will say is that being wrong about a message on your Mac and being wrong about it on someone else's server are not the same kind of wrong.
Read the whole local-first argumentTry it on the inbox you cannot risk.
macOS 14 or later, Apple Silicon. No account, no cloud classification, no setup. It filters inside Apple Mail on your Mac.
