There isn't one replacement for an in-app chat API, because the category has split three ways: chat SDKs with ready-made UI components, raw real-time infrastructure you build messaging on, and voice and video platforms that add chat. Decide whether you're shipping a finished conversation screen or building your own, then shortlist within that group.
The chat API category has split, and the product you're leaving shows it: Sendbird's own home page now leads with AI customer experience for enterprises rather than a developer chat toolkit. If you came for in-app messaging, you've got three directions to choose from, and they suit very different teams.
The nine alternatives below are in no particular order and grouped by what they give you to build with. Start with the table, then read the group that matches what you need to ship.
SDK types at a glance
| Tool | SDK type | Good for |
|---|---|---|
| Ably | Realtime platform | Chat and collaborative features on realtime messaging |
| Agora | Voice, video and chat APIs | Voice and video calls, including conversations with AI |
| CometChat | Chat SDK with UI kits | Chat plus calling with UI kits for web and mobile |
| ConnectyCube | Chat and calling SDKs | Ready-made SDKs for Flutter, React Native and native apps |
| MirrorFly | Self-hosted CPaaS | Chat, video and calling you host yourself |
| PubNub | Real-time infrastructure | Pub/sub messaging built for very large scale |
| Sceyt | Chat API | Customisable, scalable in-app messaging |
| Stream | Chat, video and feeds APIs | Chat, video, livestreams, feeds and moderation from one vendor |
| TalkJS | Chat API with pre-built UI | A finished chat UI or headless data APIs |
Chat SDKs that ship with UI kits
This is the closest swap if you want a messaging screen you can drop into your app and restyle. TalkJS gives you a pre-built chat UI, or headless data APIs if you'd rather draw the interface yourself. CometChat covers chat plus voice and video calling for web and mobile, packaged as UI kits, SDKs and APIs. Sceyt focuses on customisable, scalable in-app messaging through its chat API and SDKs.
ConnectyCube offers ready-made chat and calling SDKs for Flutter, React Native, web, iOS and Android, which helps when one small team ships to several platforms. Stream goes wider than chat, with video calling, livestreaming, activity feeds and AI moderation under one roof, so it's worth a look if chat is one feature among several.
Real-time infrastructure to build messaging on
The next two sit a level lower. Instead of a chat screen, you get the real-time plumbing underneath: PubNub runs on a pub/sub network, and Ably is a realtime platform for chat, collaborative apps and AI features. You design the conversation model, the storage and the interface yourself.
MirrorFly is the self-hosted choice here, a CPaaS with chat, video, contact centre, VoIP and chatbot SDKs you run on your own infrastructure. That suits teams with strict data rules, in exchange for running the servers yourself.
This route takes longer, but nothing in your product is shaped by someone else's idea of what chat should look like. If you'll also reach users outside the app, my guide to push notification services covers that side, and my Twilio alternatives list covers SMS and voice providers.
Voice, video and media-first platforms
Agora starts from voice and video, with chat and voice AI APIs added, plus no-code and low-code tools. It's the stronger fit when calls are the heart of the product and messaging supports them, not the other way round, including conversations between people and AI voices.
Two of the chat SDKs above also include calling, so if you need a little video inside a mostly text app, you may not need a media-first platform at all. Work out which is the main event, the conversation or the call, before you shortlist.
All nine, from A to Z
Ably
Best for: Product teams building live chat, collaborative apps or AI experiences on a realtime platform the vendor says is built for scale and reliability.
Agora
Best for: Apps where voice and video come first, with chat and voice AI APIs plus no-code and low-code tools; the vendor promises ultra-low latency.
CometChat
Best for: Developers who want in-app chat, voice and video calling for web and mobile with UI kits, starting on a stated free plan, with on-prem open to discussion.
ConnectyCube
Best for: Mobile teams working in Flutter, React Native, iOS, Android or web who want ready-made SDKs for messaging, voice and video calls.
MirrorFly
Best for: Companies that need to self-host communications, with chat, video, contact centre, VoIP and chatbot SDKs; the vendor says integration is quick.
PubNub
Best for: Engineering teams building real-time features on a pub/sub network, which the vendor calls the largest in the world.
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Sceyt
Best for: Product teams after a customisable chat API and SDKs for in-app messaging; the vendor credits a binary protocol for real-time delivery with no lag.
Stream
Best for: Apps that need in-app chat alongside video calling, livestreaming, activity feeds and AI moderation from one set of APIs; the vendor says you can start free.
TalkJS
Best for: Teams that want a pre-built chat UI or headless data APIs for one-to-one, group and AI chat, with notifications built in, per the vendor.
Advice before you write a line of code
Build a prototype of your own conversation screen in two shortlisted SDKs before you commit. Vendor demos show the happy path; your screen has your message types, your moderation needs and your offline cases, and that's where the differences show.
Treat claims about scale, latency and reliability as the vendor's claims. They may well hold up, but your load and your users' networks are what count, so test on a slow mobile connection as well as the office wifi.
Pick by need and build it this week
- A finished chat screen fast: start with the chat SDKs that ship UI kits and restyle what they give you.
- Chat plus calls in one SDK: look at the chat SDKs that include voice and video before reaching for a media platform.
- Calls first, chat second: go to the voice and video group.
- Your own data model and interface: build on the real-time infrastructure group.
- Data that must stay on your servers: shortlist the self-hosted option and check the rules for your sector, which vary by country.
- Feeds, moderation and chat together: pick the vendor that bundles them, so you're not stitching three services together.
Whichever line you're on, give it a week: a day for the shortlist, three days building the same screen twice, and the rest for testing on poor networks and real devices.
Do you make chat SDKs or real-time messaging APIs? Tool makers can ask to be considered for a featured place on this list.
Want your tool on this list? Featured spots and reviews here are paid partnerships. Here's how to partner with me.
Frequently asked questions
What's the difference between a chat SDK and a real-time API?
A chat SDK gives you messaging features, and often UI components, ready to use. A real-time API gives you the underlying delivery layer, and you build the chat logic and interface on top of it.
Do I need a UI kit?
If you want a working chat screen quickly, yes. If your design is unusual or you want full control of the interface, a headless API or real-time layer gives you more freedom.
Can I self-host in-app chat?
Yes, some providers offer a self-hosted option. You'll run and update the servers yourself, so check you have the people for it and the data requirements that apply to you.
Should chat and video calling come from the same vendor?
It's simpler when they do, since users, permissions and notifications live in one place. If calls are the core of the product, a media-first platform may serve you better.
How long does it take to switch chat providers?
It depends on how much of your app talks to the provider directly. Message history, user accounts and push settings all need moving, so plan a migration and keep a thin layer in your own code between the app and the SDK.
How do I moderate messages in an in-app chat?
Decide what you'll block, flag and review before launch. Some providers include AI moderation; otherwise you'll need your own filters and a way for users to report messages.
