beryl

Type-safe real-time channels and presence for Gleam, targeting the Erlang (BEAM) runtime.

import beryl
import beryl/presence

// Track who's online and broadcast every change to the room —
// Phoenix-compatible presence diffs, backed by a CRDT.
let config =
  presence.Config(
    pubsub: Some(ps),
    replica: "node-1",
    broadcast_interval_ms: 1500,
    on_diff: Some(fn(diff) {
      beryl.broadcast_presence_diff(channels, "room:lobby", diff)
    }),
  )

// …then, inside your channel's join callback:
let _ref =
  presence.track(p, "room:lobby", "user:alice", socket.id(socket), meta)

// ps, channels, p and meta come from your app — see the Presence guide.

Where to start

Install Add beryl and its BEAM dependencies to your Gleam project.

Quick Start Build your first channel end-to-end: server callbacks, WebSocket transport, and a Phoenix JS client.

Guides Go deeper on channels, presence, PubSub, groups, supervision, and the WebSocket transport.

API docs Generated reference for every public beryl module on HexDocs.

Features

Real-time channels

Define channels with typed callbacks and pattern-matched topics. Join, leave, and broadcast with compile-time guarantees on socket state — the Gleam compiler holds you to your own assigns type.

Presence tracking

Know who's online with a CRDT-backed presence system. An add-wins observed-remove set resolves joins and leaves automatically across distributed nodes.

PubSub on OTP

Distributed publish/subscribe powered by Erlang's pg process groups. Works across cluster nodes with zero configuration.

Phoenix-compatible wire

A JSON array wire format compatible with Phoenix client libraries, with first-class WebSocket support via Mist integration.