For journalists
A source wrote to you. That is between you and them.
Klar filters spam inside Apple Mail, on your own machine. The extension that reads your inbox holds no network permission, so what a source sends you never reaches a vendor, ours included.
Get Klar freeThe duty
The law shields you. It does not shield everyone holding your mail.
Section 10 of the Contempt of Court Act 1981 is one sentence: no court may require you to disclose the source of information contained in a publication for which you are responsible, unless disclosure is necessary in the interests of justice, national security, or the prevention of disorder or crime. It is a shield over the person responsible for the publication. That is you.
A cloud spam filter is not responsible for your publication. It reads every message on its own servers because that is where it runs, which is lawful and ordinary and not something any vendor should be implying otherwise about. It does mean a second company holds the message that names your source, under its own retention schedule, its own jurisdiction, and its own answer if someone comes asking. Your source was not told about that company, and cannot weigh it.
Contempt of Court Act 1981, section 10How Klar answers it
The filter runs where the message already is.
Klar is a Mail extension. It scores each message on your Mac as it arrives, in the same place the correspondence already sits, and writes nothing anywhere else. No provider to vet, no terms to read, no server holding the tip. Not because we did that work for you, but because it never starts.
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. We do not know who you are, which is the only durable way to hold no data about you.
- 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
A spam filter cannot identify a source. Why does this matter?
It does not have to identify anyone. To classify a message a filter reads the sender and the start of the body: that is the address the tip came from and what it says. Held on a vendor's servers, that pair is the whole thing your source was promising themselves you would keep. Klar reads exactly the same, on your Mac, and sends none of it anywhere.
My mail is hosted by my newsroom. Does this change anything?
Yes, though it is a narrower claim than it sounds. Klar only decides where spam filtering happens. If your inbox lives on a provider your desk chose, that is its own arrangement with its own contracts, and a spam filter does not touch it. What changes is that your correspondence stops being a second, quieter copy on a filtering vendor's servers as well.
Does anything at all leave the machine?
Not from the free App Store app: it has no network permission. Klar Plus, the paid companion you install yourself, uses the network in two places, a licence check and model updates. Neither one carries your mail. Sending spam samples back to improve the filter is a separate switch, and it is off until you turn it on. 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. The free App Store app sends us nothing, so there is nothing for us to process on your behalf. Our privacy policy sets out what we hold, which for the app is nothing at all. If you turn on spam sample contributions in Klar Plus, that changes, and you should treat it as a decision to review rather than a default.
Being precise
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 argumentFree, on the Mac App Store
Try it on the inbox you cannot risk.
macOS 14 or later, Apple Silicon. No account, no cloud, no setup. It filters in Apple Mail and nothing is sent anywhere.
