Chatto: Open-Source Team Messenger Built for Privacy

Teams seeking a way to move their group chats away from commercial platforms now have another option for self-hosted messaging. Chatto emerged recently when its developer released the code under an open-source license and published binaries that anyone can deploy on their own hardware. The software targets the same territory as major team messaging services, but it keeps all message data on infrastructure the operator controls.

Installation is straightforward through a single executable. An operator drops the binary onto a machine, runs it, and instantly gets a working chat server that also serves its own web frontend. Builds are available for Linux on x86_64 and ARM64, macOS, and Windows. A basic setup requires no separate database, and larger deployments can scale out with Docker Compose or Kubernetes.

What the encryption covers

The privacy model begins at the account level. Chatto encrypts message text and selected durable account fields with per-user keys. Each user’s data is locked to keys specific to that account, so the plaintext depends on keys held for that person alone. When someone deletes their account, the server performs crypto-shredding and destroys those keys. The data tied to them becomes unreadable, and recovery becomes impossible even from a backup that still holds the encrypted bytes.

This approach gives account deletion a concrete effect. A user who leaves takes the readability of their content with them, since the keys that unlocked it are gone.

Certain fields and assets sit outside the encryption boundary and remain in plaintext. The per-user keys cover message text and selected durable account fields, and that content makes up the encrypted set. Operators receive a clear record of which data the keys protect and which data the server stores in the clear, so they can measure the exact reach of the protection against their own requirements.

One server, one community

Each Chatto server runs a single community. A server holds its own users and messages and keeps that content to itself, with no federation of data across instances. This design limits how far any one conversation travels, since the messages live on one server owned by one operator. People who belong to several communities connect to each server directly from the client. An operator running more than one community starts a separate process for each. Chatto carries no third-party tracking and no analytics.

Voice and video calls come built in, with screen sharing, and use end-to-end encryption that keeps call media readable only to the participants. Call capacity depends entirely on the operator’s own hardware.

A hosted option on European infrastructure

Teams that want the privacy properties of self-hosting but prefer to hand off server operation have a hosted service on the way. Chatto Cloud will enter public beta soon, offering paid hosting for Chatto servers. It launches on European and European-owned infrastructure, a detail that carries weight for organizations with data-residency requirements in the region. More regions are planned for early 2027. Servers on Chatto Cloud stay compatible with self-hosted ones, and operators can move their data into or out of the service at any point.

Chatto is available for free on GitHub.