Why our customers choose Ably over PubNub

Ably is an enterprise-grade serverless WebSockets platform for pub/sub messaging at the edge. Our customers trust in Ably to power scalable and realtime online user experiences that will work anywhere in the world, without fail.

We provide an elastic, hyper-reliable global infrastructure that also comes with the flexible building blocks needed for creating rich user experiences. Everything is offered via consistent and intuitive APIs.

Focus on building realtime apps that delight customers. We'll handle the rest.

Ably is a serverless edge messaging platform designed to stream realtime messages at extreme scale to web, mobile, and IoT devices, over a fault-tolerant, autoscaling global edge network. We deliver 750+ billion messages to more than 300 million end-users each month.

As a managed solution, Ably enables you to:

  • Easily build high-performance realtime functionality that delights your users.

  • Reduce engineering and DevOps efforts - there's no complex realtime infrastructure for you to provision and maintain.

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Key Ably advantages vs PubNub



Global median round trip latencies of sub 65ms

Ably's round trip latencies, measured as the time taken to publish a message on one connection and receive a message on another connection, dependably range from 5ms to 200ms, with a median global latency of 65ms.

PubNub advertises sub-250ms worldwide latencies.

QoS & message delivery guarantee

Ably provides guaranteed message delivery and continuity across disconnections. Publishers only receive an ACK when data is persisted in two locations, and subscribers never lose data during brief disconnections as we maintain connection state for each client on our servers.

From PubNub: "PubNub is not a guaranteed message delivery service."

Continuity and connection state recovery

Ably provides continuity for clients that become disconnected for reasons such as going through a tunnel or changing networks. We store the connection state for each client on our servers so that clients that reconnect within two minutes can resume their connection and receive all messages published whilst they were disconnected.

PubNub does not store connection state but does queue up to 100 messages upon disconnection, and can 'catch' clients back up on those messages upon reconnection. From PubNub: "The default message queue size is 100 messages. Consequently, publishing past 100 messages inevitably results in older messages overflowing the queue and getting discarded."

Reliable message ordering

Ably ensures that messages are delivered to persistently connected subscribers in the order they were published on each channel using the First-in-First-Out (FIFO) pattern.


Idempotent message publishing

Ably supports idempotent publishing across all our native client library SDKs.


Delta Message Compression

Ably supports message delta compression on a per channel basis.

PubNub does not support message delta compression.

Server-Sent Events (HTTP Streaming) protocol support



JSON Web Token support

Ably allows for not only Ably Tokens to be embedded within JWTs, but also for JWTs to be signed by Ably API keys and used themselves for authentication.


Configurable private key permissions

Ably provides support for private API keys with configurable permissions including restrictions on channels or operations.

PubNub does not provide configurable private key permissions

Robust features set to power delightful realtime experiences


Publish messages to millions of subscribers over Ably channels - named units of distribution that offer a way to implement Pub/Sub messaging and realtime data delivery.


Ably supports WebSockets, SSE, and MQTT, so you can choose the right protocol for your use case. We also support the Pusher and PubNub protocols, making the migration to Ably quick and simple.


No message is ever lost, delivered multiple times, or out of order, even if unreliable networks and brief disconnections are involved.


Subscribe to events when devices or users enter, leave, or update their state on channels. Essential for use cases like chat, multiplayer games, or collaboration tools.


Reduce the bandwidth needed to distribute messages to consumers by sending only the changes from the previous message instead of the entire payload.


Send push notifications over Ably channels, or deliver them directly to Android and iOS users with FCM and APNs.

Simple and powerful client library SDKs

All official Ably client library SDKs offer a consistent yet idiomatic API across every language. Regardless of your development environment or preferred language, Ably keeps things simple for you by providing consistency and predictability. You can quickly integrate our SDKs into your tech stack with a few lines of code, and start building realtime features in minutes. 

Migrate to Ably

Ably is the only cloud vendor that supports the PubNub protocol. It’s simple to migrate to Ably, or use Ably as a failover for PubNub in hours instead of months.