Compared to alternatives

Concord is not the only way to do private messaging on Nostr. It is built for one specific shape — large, Discord-style communities — that the others do not target. Each alternative below is genuinely better at something.

NIP-17: private direct messages

NIP-17 is the standard for encrypted DMs on Nostr, and it is the right tool for one-to-one conversation.

It cannot do communities. Multi-member rooms are an afterthought in the design, and the recipient-addressed model is vulnerable to denial-of-service issues: because everything is p-tagged at you, your client must decrypt your whole giftwrap inbox to find anything.

Concord’s stream inversion — fixed author, ephemeral p tag — is precisely what makes a room subscribable with one filter instead of a full inbox scan.

NIP-29: relay-based groups

NIP-29 puts groups on a relay that enforces membership and moderation.

Two consequences follow. You have to self-host an entire server just to start a community, and messages are not end-to-end encrypted — the relay reads everything, because it has to in order to enforce anything.

Concord needs no server: relays see only noise, and authority is a signed roster every member verifies for themselves. The cost is that enforcement is by rejection rather than prevention, so a misbehaving member can always publish; they just cannot be obeyed.

Marmot: MLS on Nostr

Marmot uses MLS for forward secrecy and post-compromise security. For small, high-stakes groups this is the stronger choice, and Concord does not try to match it.

MLS advances in lockstep: ordered commits, per-device key packages, and a cost per membership change that grows with the group. That is exactly the wrong shape for a large, casual, high-churn public room where people join and leave constantly and half the members are offline at any moment.

Concord trades those ratcheting guarantees for asynchronous, fold-anytime state. A member who has been offline for a month opens their client and converges without a coordinated commit from anyone.

Iris Chat: Double Ratchet

Iris Chat applies the Double Ratchet to Nostr conversations, for much the same reasons as Marmot. It aims to replace Signal more than Discord: pairwise ratcheted chats rather than owner-rooted communities.

The summary

NIP-17 is for DMs. NIP-29 trusts the relay. Marmot and Iris Chat secure the small ratcheted group. Concord is built for the scale and shape of a public community.

If your group is six people planning something sensitive, use a ratcheted protocol. If it is six hundred people with channels, roles, and moderators, that is what Concord is for.

Interoperability

These are not mutually exclusive choices for a client. Armada, for example, speaks Concord alongside NIP-29 and Buzz communities, so one key logs you in across the ecosystem and your communities come with you where clients share protocols.