Migrate from Ably to NoLag

Ably is a mature realtime platform with rich delivery semantics. NoLag shares the same pub/sub foundation and presence model, so moving across is mostly a matter of renaming a few concepts. This guide maps Ably onto NoLag and shows the same flow in both.

Why teams move

NoLag keeps the realtime transport you rely on and adds:

• Blueprint SDKs for chat, notifications, dashboards, tracking, and more.
• A coordination layer for AI agents: dispatch, share state, observe, and approve, on the same platform as your app features.
• One place for human-facing and agent-facing realtime.

Concept map

Before: Ably

import * as Ably from 'ably'

const ably = new Ably.Realtime('API_KEY')
const channel = ably.channels.get('chat')

channel.subscribe('message', (msg) => {
  console.log('Received:', msg.data)
})

channel.publish('message', { text: 'Hello!' })

After: NoLag

import { NoLag } from '@nolag/js-sdk'

// Create the app and its `general` room in the control plane first. The app
// slug you get back has a random suffix (for example `chat-a3f9`): that is
// what you pass to setApp(). Room slugs are kept verbatim.
const APP_SLUG = 'chat-a3f9'

// One actor subscribes...
const receiver = NoLag('receiver_access_token')
await receiver.connect()

const inbox = receiver.setApp(APP_SLUG).setRoom('general')
inbox.subscribe('message')
inbox.on('message', (data) => {
  console.log('Received:', data)
})

// ...and another publishes. Publishers never receive their own messages,
// so a single client that subscribes and emits will not log "Received".
const sender = NoLag('sender_access_token')
await sender.connect()
sender.setApp(APP_SLUG).setRoom('general').emit('message', { text: 'Hello!' })

One behavioural difference from Ably is worth flagging before you port a test suite: an Ably client sees its own publishes, a NoLag actor never does. Append the sent message to your UI locally, and use a second actor in tests that expect to receive.

Presence and history

Ably presence maps to NoLag presence, tracked per room with join and leave events and a live member list. A client sets its presence on the room with room.setPresence(data) and listens for presence:join, presence:leave and presence:update on the client.

History is the one Ably feature that does not have a direct counterpart. NoLag is a messaging layer, not a database: a client that reconnects gets its subscriptions restored and nothing replayed, and a fresh subscription receives no history. If you use Ably history to fill gaps after a disconnect or to render the last N messages on load, keep those messages in your own store and read it on connect. The one place the broker does replay is for load-balanced worker groups with persistent sessions, which is a different job; see Replay and Durable Delivery for exactly what that covers.

Delivery guarantees

Ably is known for its delivery semantics. NoLag offers quality-of-service levels 0, 1, and 2 per message, chosen on each emit rather than paid for everywhere. Be precise about what they cover: the level governs the hop across NoLag's internal broker, and the WebSocket leg between your client and NoLag has a simpler contract. A publish can be acknowledged (pass a callback to emit and it resolves on the broker's published ack), nothing is resent for you, and there is no exactly-once guarantee end to end. Put an idempotency key in the payload of anything that must not be applied twice.

Authentication

Ably authenticates with API keys and tokens, often carrying capabilities in the token itself. NoLag centres permissions on the actor: every credential resolves to a typed actor (user, device, service, session, agent, orchestrator or observer), and its read and write access lives server-side as per-topic ACL rather than in each token. For browser clients, your backend mints a short-lived JWT (client token) signed with a project signing key, so long-lived credentials never leave your servers.

Next steps

• Start with the 5-minute quick start.
• Read the deeper NoLag vs Ably comparison.
• Explore the high-level SDKs if you would rather not rebuild chat or dashboards by hand.