The Technical Side of Push Notifications: What Are They, How They Work, and How to Set Yourself Up for Success

In today’s cluttered, fast-moving marketing landscape, push notifications are a key tool for brands looking to cut through the noise and grab their customers’ attention. But while most marketers are aware of push notifications, that awareness doesn’t necessarily translate into comfort with the technical side of this powerful messaging channel.

To help out, we’re going to take a look at push notifications, exploring what it takes to be able to send these messages, how brands can ensure that they’re able to deliver push at scale, and other key technical considerations.

What Is a Push Notification?

A push notification is a pop-up message that’s sent to users’ mobile device—or, in the case of web push, to your laptop or desktop computer—by a mobile app (or website) they’ve given permission to message them. Unlike more passive message types like in-app messages or Content Cards, a given user doesn’t need to be actively using an app or website in order to receive this kind of alert. That means that push is a great channel for timely, urgent content intended to inspire a user to start a new session or take a specific action.

Push notifications can take a number of forms, from simple updates on the status of a recent order...

...to eye-catching notifications leveraging rich content like images, GIFs, sounds, or push action buttons.

The key with push notifications is that they’re attention-grabbing by nature. They’re a great way to ensure that your audience knows about breaking news or a big new sale or any other essential, time-sensitive communications, but they can also be overwhelming if you send too many (or send pushes that aren't relevant or valuable to the recipients). So be thoughtful about what you send and whether push is the right channel to send it in—after all, there are a lot of other channels out there.

How are Push Notifications Actually Sent to Devices?

In general, there are two ways for a marketer (or editor, in the case of a news brand) to serve up a push notification to their audience members’ devices: They can either create a push notification via the user interface or dashboard of a customer engagement platform like Braze or send these messages directly through API calls.

That first, dashboard-based approach is probably the one that marketers would take in most situations. They’d create a blank message, drop in the relevant copy, choose whether or not to include rich content like images, identify what audience segments they’re looking to target, or what behaviors they might want to use to trigger the message, and then—when it’s ready—use the dashboard to send (or schedule) the message.

The second approach, leveraging API calls, is ideal for highly time-sensitive messages. Some brands use this approach to automatically send a push notification whenever their CMS publishes an article. We’ve also seen brands use this approach during elections to allow notifications about the results of local races to be sent out as fast as possible. Instead of creating each push notification in an ad hoc manner, news brands were able to pre-build push notifications based on different potential outcomes and when their Decision Desk called a race, all they had to do was tap a button signalling which candidate had won and the correct push was sent immediately, ensuring that fastest-possible delivery to users.

But while these two different approaches are quite different on the surface, if you look under the hood, they’re fundamentally pretty similar. All push notifications are sent via Apple Push Notification service (APNs) for iOS devices and Firebase Cloud Messaging (FCM) for Android devices. These services effectively serve as gatekeepers for brands looking to send push notifications to their users and each have their own specific requirements for sending that marketers are required to respect.

One of the key requirements? Push tokens.

What’s a Push Token?

A push token is a device-specific identifier that APNs and FCM assign in order to create a connection between an app and an iOS, Android, or web device (that is, a smartphone or computer). You can think of a push token as a flag that alerts the push sending service that this device has subscribed to receive push messages. The upshot? It’s impossible for marketers to send push notifications to a device that doesn’t have a valid push token assigned to it.

It’s important to know that there are actually two halves that make up each push token: Foreground and background tokens.

Foreground Push Tokens

Foreground push tokens are required for a push notification to be displayed on a particular device. When a user opts-in for push notifications, then that specific device is enabled to receive push and is provisioned both a foreground and background push token from APNs or FCM. (There are some wrinkles here around provisional push notifications—to get the full scoop, check out our provisional push overview.)

Background Push Token

Background push tokens are assigned to all devices that have a brand’s app downloaded, whether or not that particular device has opted-in to receive push notifications from that brand. These tokens allow brands to send silent push notifications—that is, push notifications that intentionally won’t be displayed—to devices in order to support key functionalities like uninstall tracking.

It's possible that a user’s device may have a background push token but not a foreground push token. For example, if a user opts out of push notifications but still has the app downloaded, then that device will only have a background push token. Similarly, if a user uninstalls the app, then their device will no longer have any tokens associated with that app—which, as you might expect, means that no future push notifications will be delivered.

How Can Brands Send Push Notifications Quickly (and Successfully) at Scale?

When your brand is working with a customer engagement platform or other push provider, it’s essential to make sure that it can send push notifications promptly and to your total eligible audience. While most brands won’t want to hit their entire audience with blast push notification campaigns too often, there are times when the ability to reach everyone in this channel is essential—think significant breaking news, notifications related to natural disasters or crises, and other high-importance situations.

For customer engagement platforms, supporting those kinds of sends for a large number of brands can mean supporting a large number of messages. At Braze, for instance, our platform sent 1.4 billion push messages on 2019’s Black Friday and Cyber Monday alone across our global client base. Supporting that kind of volume required an extremely robust infrastructure to process and dispatch push notifications to APNs and FCM efficiently at scale.

That need is a key detail to remember when you’re looking to implement real-time messaging for your business—if your brand will be reacting to global events or tentpole events and holidays by sending large-scale campaigns, remember that you won’t be alone and that your chosen customer engagement platform needs to be built to keep up. In situations like this, the speed and scalability of the tools you use really matter. (To learn more about how Braze solved these scalability issues, check out this piece from Braze Cofounder and CTO Jon Hyman.)

On the other side of the coin, we’ve seen brands invest in scalable customer engagement platforms and send massive push campaigns—only to discover that the sheer amount of traffic that they’ve generated is more than their app or website can support. If you anticipate that one of these large campaigns could potentially drive a spike in user activity that could overload your servers, the smart move is to start rate limiting your campaigns. Rate limiting allows brands to set message-sending limits on a per-minute basis (so, for instance, delivering a campaign over a five minute period to your audience of five million users, instead of delivering to all of them in a single second) in order to evenly spread out delivery of a push campaign to your audience...and add a layer of control to the potential increase in traffic.

Final Thoughts

Push notifications are a powerful tool for customer engagement—but they’re a tool that stands on a foundation provided by technical compliance with services like APNs and FCM and your chosen customer engagement platform’s scalable infrastructure.

Interested in digging a little deeper into the technical intricacies of push notifications? Check out our push best practices, client integration gallery, case studies, and Brilliant Experiences by Channel guide.