Give someone a way to reach you. Take it back when you want.
Kontaks is private 1:1 and group messaging, voice messages and calls with no phone number and no username. Nobody can contact you unless you handed them a way in, and you can destroy it from your side alone.
Not released yet. Kontaks is in development for iPhone and Android.
A contact you cannot give away
A phone number is one address that reaches you from anywhere, held by everyone you have ever given it to. You cannot take it back, and neither can they. Kontaks replaces it with something narrower: a way in that one person holds, that works only from their device, and that you can end.
No number, no username
There is nothing to look up, nothing to guess and nothing to publish. No directory, no search for people, no profile page for yourself.
Reachability you issue
A contact is created only by pairing. Forwarding it to someone else does not work: the way in is bound to the key on that person's device.
Revocable from one side
Delete someone and the line is gone, both directions, immediately and permanently. No notification, no appeal, no reinstatement.
One caveat we state rather than bury. An invite that is still in flight is a bearer credential: until it expires, is used up, or you revoke it, whoever holds it can redeem it. An established contact cannot be handed on; an unredeemed invite can.
Run a group without everyone holding everyone's number
When a club, team, class or committee starts a group chat, every member ends up with every other member's mobile number. Someone who leaves keeps all of them, forever, and nobody can undo it.
- Start the group. Name it. There is no account to make and nothing to sign up for.
- Show one code. Members scan it in turn, and each scan puts that person in the group directly.
- Nobody exchanges a number. Members can message and call inside the room without holding any address for each other.
- Remove someone and they are gone. Not muted, not blocked. They lose the room and every group-scoped line with it.
What Kontaks does not do
We never upload your contact book
Not to match you with anyone, not to suggest friends, not ever. There is no "people you may know" because there is no way to build one.
We do not store your contacts, and we never see their names
The name you present travels inside end-to-end encryption to the one person or room you chose. No collection on our servers has a field for it. What the servers can and cannot infer is set out in full on the security page.
No presence, no last seen, no read receipts
We never show when you were online, when you read something, or when you are typing. None of it is built.
No analytics SDKs and no ads
No third-party analytics, no advertising SDK, no tracking, on the app or on this website. This page loads no font, script or image from anywhere but kontaks.io.
How it is built, stated precisely
We describe what we built. We do not guarantee outcomes, and we do not claim a review we have not had.
- 1:1 sessions use libsignal, the Signal Protocol implementation itself, rather than a reimplementation of it. Group messaging is pairwise fan-out of those 1:1 sessions — it is not Signal's group protocol, and there is no sealed sender.
- Calls are DTLS-SRTP with the fingerprint signed by the key that the two of you established when you paired, so a substituted fingerprint fails verification.
- Messages are deleted from our servers the moment they are delivered, and after seven days if they are not.
- Kontaks has not been independently audited. When that changes we will say so here, with the report.
Read the full threat model, including what Kontaks does not defend against.
Before you install
Kontaks is not a phone
You cannot call 911 or any other emergency service from Kontaks. It has no carrier connection and no route to an emergency dispatcher. Keep your regular phone service for emergencies.
Adults only, and it needs an internet connection
Kontaks is 18+. There is no SMS fallback, by design, because an SMS fallback would need a phone number — so with no data there is no Kontaks.