5 Best Instant Messaging APIs

Looking for the perfect instant messaging solution can be a daunting task.

You need a provider that not only supports all the necessary instant messaging features but also offers delivery and scaling guarantees to ensure a smooth chat operation as your business grows.

While it might be tempting to start with a simple solution and see how your needs evolve, underestimating the importance of finding the right provider can be a costly mistake. Switching solutions later requires significant time, resources, and money, not to mention meticulous testing to avoid disruption to your business, which can lead to reputational damage and lost revenue. You need to get it right the first time, and this post is here to help you do exactly that.

We've narrowed it down to just the 5 best instant messaging APIs and SDKs, taking into consideration factors like features, scalability, and price. This way, you can make an informed decision about which provider will work best for your project.

What are instant messaging APIs and SDKs?

Fundamentally, instant messaging APIs and SDKs enable developers to build instant messaging more quickly by managing the infrastructure necessary to send and receive messages in realtime, plus must-have chat features like typing indicators, online indicators, and read receipts.

If you’re wondering how an API and SDK differ in this context, it has to do with how developers interface with said infrastructure.

An API gives developers direct access to the infrastructure through endpoints to send and receive messages, subscribe to typing indicators, and more. Equipped with the nuts and bolts, developers can now implement a chat UI with total flexibility.

An SDK, on the other hand, offers a complete set of development tools, usually including prebuilt chat UI components. By assembling chat “building blocks”, developers can save time up front.

Remember that APIs and SDKs aren’t mutually exclusive, and some providers offer both.

What should you look for in an instant messaging solution?

Instant messaging apps like WhatsApp and Slack have set the bar for instant messaging experiences, and it’s important to find a provider that enables you to deliver the same quality experience.

These are the ten foundational features you have to be able to deliver using your chosen solution, and that you should consider during your evaluation process.

• Low Latency: If messages take too long to send or load, users won’t have a smooth user experience and will take the conversation elsewhere. That could be another channel (for example, a customer might pick up the phone and start their support request from scratch) or, if the experience is consistently laggy, users might even switch to another app.

• The ability to scale: As your user volume grows, the load on the server also increases. If the server can’t handle this increased load, messaging features can become unresponsive, causing a poor user experience.

• Reliability: Even a short downtime or an occasional error can be frustrating for users. This is unfortunate, but for businesses that rely on chat applications for customer support or sales, downtime can result in lost revenue or missed opportunities.

• Guaranteed delivery: Messages should be delivered exactly once and in the correct order, even in the face of network issues. Otherwise, messages might come flying in out of order, and more than once, making it almost impossible to discern what is trying to be communicated.

• Elasticity: Instant messaging app usage can be unpredictable. Applications may experience sudden spikes in usage during peak hours or events, or during product launches and marketing campaigns. If the server can’t scale its resources up dynamically in response to changes in user demand, chat features may become unresponsive.

• Rich features: Your users will expect typing indicators, online status indicators, read receipts, push notifications, and more. If users can’t accomplish what they need to with your chat, they might switch to another app where they can.

• Integrations: Instant messaging solutions need to integrate with the other tools in your tech stack. Dedicated integrations between technologies can help keep engineering requirements to a minimum.

• Data governance: The way data is stored, processed, and disposed of needs to meet regulatory requirements, wherever you operate.

• Chat moderation: Messaging experiences need to be safe for both end users and chat operators. The process of monitoring and controlling user-generated messages helps ensure compliance with your terms of use.

• Frontend UI: Customizable themed components including colors and fonts help to keep your chat solution a cohesive part of your customer experience.

Another key consideration when evaluating a live chat solution is, of course, cost.

Most instant messaging API providers base their pricing on the number of monthly active users (MAUs). Some also account for additional factors like the number of messages and concurrent users.

While it might be hard to predict your precise usage up front, you should evaluate how a given provider’s pricing model might scale for your project. For example, some pricing models get gradually more expensive as you grow, while others hit an inflection point.

Now that we’ve covered the fundamentals, let’s look at the 5 best instant messaging APIs on the market.

The 5 best instant messaging APIs and SDKs

1. Ably

Ably is a realtime experience infrastructure used by companies like HubSpot, I7Live, and Riff to build feature-rich and reliable chat.

With the Ably API, you get the nuts and bolts needed to implement chat your way. For example, publish and subscribe functions to send and receive messages in a 1:1 or group setting, as well as additional data like which users are typing. Ably also provides other essential features, including presence to see who’s online, message history, and push notifications, and they all work cross-platform, enabling you to deliver a consistent experience across the web, Android, and iOS.

Whether it's a fundamental feature like threads, a contact book that needs to integrate with your database, or even live stream chat with donations, Ably's flexibility extends beyond customization options, allowing you to create engaging chat experiences beyond what's typically possible. Further, because you’re building on the Ably platform, you’ll benefit from low latency, guaranteed message ordering, and an assuring 99.999% average uptime SLA.

Although the nuts and bolts provided by Ably are perfect for chat, they’re not limited to chat alone. That’s great news because once you get started with Ably, you can use the same foundations to build other realtime features, including notifications, and realtime collaboration.

2. Twilio

Twilio is a communication platform with a suite of products designed to help developers code communication features like SMS, email, video, and - you guessed it - instant messaging.

Their chat product is called Conversations API and it’s unique because it’s specifically designed to enable omni-channel messaging.

Suppose your project revolves around connecting members from your team with customers. With Conversations API, the customer can start a conversation in-app then continue it on WhatsApp, for example. Twilio helps connect the dots, creating a seamless omni-channel experience on both sides.

Although Conversations API could be adapted to enable your users to chat together, that isn’t really the intended use case. As a result, Conversations API offers a limited chat feature set compared to some alternative solutions. For example, you can’t use Twilio to implement public group chat, and they don't support @user and @channel mentions or reactions.

3. Firebase

Firebase is an app development platform backed by Google that famously replaces the need for a backend. It accomplishes this by providing developers with a variety of services, including authentication, push notifications, and a database called Cloud Firestore that can be adapted to store and broadcast chat messages in realtime.

Firebase can be an attractive option because it manages all of your backend services in one place. These services are meant to gel well together, and it should therefore be smooth to implement user management, roles and permissions, chat history, and even push notifications under the roof of one platform. Of course, this might not be so compelling if you already have a backend and user management system. In that case, you’ll probably want to assess how you’ll keep Firebase and your systems in sync instead.

Remember, since Firebase is a general-purpose platform, it doesn’t have a specific notion of instant messaging. While implementing basic messaging might be fairly straightforward, expect to invest a significant amount of upfront development to get features like typing indicators, read receipts, and presence indicators to work, especially without a hitch at scale.

4. Sendbird

Sendbird Chat enables developers to implement chat and instant messaging by providing an SDK with ready-made chat UI components. They cover all the essential features you might expect, including voice and video, which makes it possible to deliver a comprehensive experience.

This out-of-the-box experience enables developers to “turn on” chat quickly, albeit at a recurring monthly premium. A common concern about Sendbird is that, beyond a certain scale, their pricing becomes somewhat opaque. This can make it hard to calculate precisely how much you’ll pay, especially if you’re dealing with a high number of users and traffic spikes.

Under the hood, Sendbird manages the chat infrastructure necessary to send and receive messages in realtime while ensuring that messages are stored securely and compliant with relevant standards like SOC 2 and HIPAA.

It should be noted that although Sendbird touts eight available data centers, each app must reside in a single data center, creating a single point of failure. Moreover, this can negatively impact latency, unless your users happen to be connecting from the same geographical region.

5. Stream (formerly GetStream)

Stream provides APIs and chat UI components that developers can use to implement instant messaging into their web and mobile applications.

They make it possible to build chat experiences with rich features like typing indicators, user presence, threaded conversations, push notifications, message & user moderation, reactions, plus @user and @channel mentions. In other words, everything you need for a modern chat experience.

All the infrastructure is managed for you. However, all traffic is processed and stored in a single data center. This can have a negative implication on latency and creates a single point of congestion and failure. This might explain why Stream only offers a 99.95% SLA unless you pay more for an enterprise plan.

It’s worth noting that instant messaging often goes hand-in-hand with other realtime use cases, such as multiplayer collaboration (think of a product like Figma, where you can edit your design collaboratively and chat with other users in realtime). However, Stream is very much a chat-centric solution. If you’re looking to build other realtime experiences alongside your messaging functionality, Stream can’t help – you will have to use different technologies, which brings additional complexity and increased costs to your project.

Which is the best instant messaging solution for your use case?

Like everything in software, the answer is “it depends” - on the features you need, how you envision your users engaging with your app, and on if you want to save time up front with a turn key solution at the cost of flexibility later. It’s critical to try and answer these questions early on so you don’t end up locked-in with a vendor, or with a solution that is great for chat but forces you to source another solution to implement other realtime features like presence indicators, multiplayer collaboration (a la Figma), collaborative whiteboarding, and collaborative text editing.

Although we might be biased, if you are looking for a solution that can support you now - as you integrate chat - and as you scale, and introduce new features, we recommend trying Ably for free (no credit card required). Our free plan includes:

• 6M monthly messages
• 200 peak concurrent channels
• 200 peak concurrent connections

As a realtime Platform as a Service (PaaS), Ably gives you the infrastructure and tooling to build featureful in-app chat with no scale ceiling, low latency, predictable pricing, and 99.999% SLA. The best part? A new realtime feature doesn't require you to rebuild your entire back end or code against a brand-new API.

Whether it's a fundamental shift in how your product works, such as implementing multiplayer collaboration, or you want to enhance the experience through a feature such as in-app messaging, Ably makes it easy to get started thanks to integrations with almost every popular programming language and a free developer account.