Pusher vs WebSockets: Pros, cons and key differences

WebSockets are a low-level communication protocol used to enable two-way realtime communication between apps. 

Meanwhile, Pusher Channels is a commercial in-app messaging platform that happens to use WebSockets as the primary transport under the hood. 

Anything you can accomplish with Pusher, you can accomplish with WebSockets, except because Pusher is a platform, you benefit from additional capabilities and features that you’d otherwise have to implement yourself, allowing you to ship to production more quickly and with greater confidence.

Instead of burdening the challenges of scaling WebSockets yourself, with a hosted platform like Pusher, you choose a geographic location (cluster) to host your app and the platform manages it all for you.

When you use Pusher, the idea is that messages flow just as reliably and quickly whether you have one connection or one million, however, because Pusher routes messages through a centralized location, this can have an adverse effect on uptime and latency, especially when you have users connecting from around the world. 

On this page, we'll compare Pusher and WebSocket in more detail - and cover how Pusher compares to distributed alternatives like Ably Channels.

WebSocket is a communication protocol and web API that enables efficient two-way communication between apps. 

They’re usually used in web apps (hence their name), but WebSockets also work on mobile, making them an attractive option for building cross-platform products with realtime features.

Compared to HTTP where the client initiates requests over a short-lived connection, WebSockets work by establishing a long-lived connection between the browser and the server, allowing either side to send fresh data as soon as it’s ready with minimum overhead. 

This makes them a great choice for situations where two-way communication is needed such as chat and multiplayer collaboration.

Additionally, WebSockets are well-suited when you need to push frequent one-way updates from the server to the client - like live sports score updates, updates on package delivery, fresh chart data, or perhaps a stock ticker for a new cryptocurrency. 

Because WebSockets are a low-level transport, they require additional work on top to enable efficient and reliable realtime communication. 

Here are a few examples of things you’d need to implement on your own: 

• Authentication and access control.

• A pattern like Pub/Sub to route messages to specific subscribers, such as members of a chat room.

• A heartbeat to detect disconnections.

• And a mechanism to automatically reconnect and resume missed messages.

Rather than reinvent the wheel every time you need WebSockets, it’s generally more productive to use a WebSocket library such as Socket.IO, however, features are just one half of the WebSockets-in-production equation. 

The other - much harder - part is how to deploy and manage the WebSocket code so that messages always get where they need to go, exactly once, with minimal latency, and without risk of data getting lost in the process. 

WebSocket connections are inherently fragile because they depend on a long-lived connection that can be interrupted at any time - for instance, if the end-user goes through a tunnel. 

When disconnections happen, you not only need to reconnect as quickly as possible, but resume missed messages as well. Holding on to undelivered messages on the backend contributes to backpressure, and this can be a tricky problem to solve, especially at scale. 

Did you know? In some cases, enterprise networks such as schools and governments sometimes block WebSocket connections due to stringent firewall policies. When that happens, you need to fallback to an alternative transport such as HTTP long polling. Said another way, if you want a really robust messaging layer, you need a fallback, but that requires a totally different approach.

Another symptom of WebSockets needing a persistent connection is they’re challenging to scale. 

Long-lived connections are inherently more resource-intensive compared to short and bursty HTTP connections, which only live for the duration of the request. 

You might be tempted to throw more resources at a server however, this can only take you so far.

• Eventually you will hit the hardware limits of one server (or it will become very expensive).

• A single server is prone to downtime and data loss, as there is no redundancy in place in case the server crashes.

At some point, you will need a way to evenly distribute WebSocket connections over multiple WebSocket servers using a load balancer, however, this incurs additional engineering complexity as you now need a mechanism to synchronize state between backend servers. 

Pusher is a commercial in-app messaging platform that uses WebSockets under the hood.  

They offer idiomatic libraries to send and receive realtime messages, saving developers time upfront by providing a general-purpose WebSocket solution.

The infrastructure part is all handled for you so, in theory, you never have to worry about connection reliability, scale, or handling an influx in connections - for example, during a launch or seasonal event.

A good way to think about realtime services like Pusher (or Ably) is like Twilio for SMS, Stripe for payments, or SendGrid for transactional email - while you might be able to implement a contrived version of these services by following a tutorial, there’s always a substantial amount of work needed to to make things work reliably in production. 

In many ways, the key features of Pusher are remedies to the challenges of rolling WebSockets yourself. Additionally, Pusher supports push notifications. 

• Pub/Sub messaging: With Pusher, you set up channels that client-side applications subscribe to. That could be one-to-one (such as a private chat between two individuals) or one-to-many (such as broadcasting financial data to subscribers).

• All the basic WebSocket features you need: Heartbeat, automatic reconnection, presence channels, and more. When you use a service like Pusher, all the essential features are included out-of-the-box, saving development time upfront.

• Managed WebSocket connections: Pusher handles the WebSocket connections for you, meaning you can focus on the features important to your application instead of finicky realtime infrastructure. 

• Push notifications: Alert end users through native iOS and Android push notifications.

Yes, Pusher uses WebSockets whenever possible to enable full-duplex bidirectional communication between subscribers.

In cases where a WebSocket connection can’t be established because of a stringent firewall, Pusher will fallback to alternative, less efficient (for realtime) protocol like HTTP. 

Pusher is praised by developers for its intuitive libraries and helpful documentation. 

It’s also considered a plus Pusher has an adjacent product, Beams, to enable push notifications (they tend to go hand-in-hand with realtime messaging).

However, since being acquired by MessageBird in 2020, Pusher feature development has slowed down while other realtime solutions on the market have sped up. 

In an upcoming section, we’ll look at a three-way comparison between Pusher, WebSockets, and an alternative realtime API (Ably) so you have a reference point for what it is you might be specifically missing. 

With Pusher, you choose a single data center through which to route all messages. For example, you might pick the EU (Ireland) cluster. 

This is problematic for several reasons: 

• Increased latency: Most applications have users distributed around the world. If you host your Pusher instance in Ireland but two users in Japan are sending messages back and forth in a one-to-one chat, for example, they would all go to London and back, incurring a laggy amount of latency. This is in contrast to a distributed alternative where data is always routed through entry points geographically closest to your clients.

  • In scenarios where one user is connected in London and the other user is in Japan, there is no way around it - data has to traverse the global network. However, there are optimizations available to ensure the message takes the shortest path through the network with minimal latency. 

• Single point of failure: Limiting the application to a single instance eventually leads to downtime and data loss.
  

To show you how Pusher and WebSockets compare specifically, and how Pusher compares to distributed alternatives like Ably Channels, we’ve included a comparison table below. 

Until now, we’ve compared Pusher and WebSocket. On one hand, WebSocket is a lower-level and customizable protocol for realtime communication. On the other, Pusher gives you the infrastructure to build realtime systems, but it lacks some realtime features and stability guarantees you probably need.

We think it’s important you see how Pusher stacks up against a distributed and featureful alternative, so we’ve made reference to Ably in the comparison table above as well. 

In summary, Ably has quality of service guarantees such as guaranteed message ordering and exactly-once delivery semantics that Pusher can’t offer.

Additionally, Ably has been architected from the ground up to offer a globally distributed realtime infrastructure that gives you and your users the lowest possible latency, while also maintaining the highest degree of uptime.

Here are some of the benefits of building with Ably:

• Global edge network with latency-based: Routing ensures messages take the shortest possible path through the network to minimize latency. While Pusher doesn't report on latency numbers, Ably offers a global median round trip latencies of sub 65ms.

• Data integrity and guarantees: Ensures there’s no need to handle missed, unordered, or duplicate messages.

• Redundancy and fault tolerance: Ensures sufficient redundancy at a regional and global level to guarantee continuity of service even in the face of multiple infrastructure failures. While Pusher can only offer 99.95% uptime SLA (equivalent to 21 minutes of downtime a month), Ably offers the highest possible 99.999% (26 seconds downtime a month).

• Elasticity and autoscaling: Ably is meticulously designed to be elastic and highly-available, providing the uptime and elastic scale required for stringent and demanding realtime requirements.

As part of your evaluation of realtime options, explore our documentation to find out more and get started with a free developer Ably account.