Best chat APIs and SDKs in 2026: what each one builds for you, and what it costs
The question that sorts chat APIs is how much of the chat you'll still build after you sign up. Sending a message isn't the hard part. The work is the chat screens, notifications to users who are offline, message history and moderation. TalkJS (that's us) ships all four on every plan, and among the APIs that ship a chat UI and price per monthly active user, it costs the least at both 10,000 and 25,000 users.
How much of the chat does each API build for you?
A chat API sends and stores messages through a server you don't run. A chat SDK is the code you add to your app to use it, and some SDKs include the chat screens too. (More on the difference in what is a chat API.)
Which chat APIs come with a ready-made chat UI?
TalkJS ships a whole chat UI: an inbox, a chatbox and a popup that you theme to match your app, with SDKs for JavaScript, React, React Native, Flutter, Vue, Angular and Web Components (see the pre-built UI). Email, SMS and push notifications reach users who are offline, and a reply to an email lands in the chat (SMS is charged separately). Every message is kept on every plan. Moderation covers a profanity filter, user reports and bans. Content suppression can also hide the phone numbers, email addresses and links people swap to take a deal off your platform.
It's built for chat between your users: buyers and sellers in a marketplace, or students and teachers in an edtech app. Mobile apps get the chat UI through the React Native or Flutter SDK, and on a website it drops into the page as React components or Web Components. TalkJS is ISO 27001 certified and GDPR compliant, with servers in the EU, and the people who answer support are engineers on every plan (chat during office hours on Basic).
CometChat sells UI kits for React, React Native, Angular, Flutter, iOS and Android, and voice and video calling as well as chat. Email and SMS notifications and AI moderation come with its higher Advanced plan, not Basic. TalkJS vs CometChat
Sendbird sells UIKits for iOS, SwiftUI, Android, Jetpack Compose, React, React Native and Flutter, plus AI customer service products. TalkJS vs Sendbird
Stream sells UI SDKs for React, React Native, Flutter, iOS, Android and Angular, with a moderation dashboard on every plan. Besides users, its plans also count stored messages, concurrent connections, API calls, bandwidth and CDN use. TalkJS vs Stream
Ably Chat has a React UI Kit and SDKs for JavaScript, React, Kotlin and Swift. It bills by activity, not by user: every delivery to every subscriber, every history read and every typing heartbeat counts as a message. TalkJS vs Ably
QuickBlox includes chat UI kits on its cloud plans. QuickBlox alternative
Which chat APIs leave the UI to you?
PubNub is real-time infrastructure with a headless Chat SDK. Its React and React Native UI kit, Chat Components, has been unsupported since January 1, 2025, so you build the screens. TalkJS vs PubNub
Twilio Conversations, which Twilio's docs now call Conversations (classic), has SDKs for JavaScript, iOS and Android and no UI kit. One conversation can mix in-app chat with SMS, WhatsApp and Messenger, and media storage and SMS fees are billed on top. TalkJS vs Twilio
Which chat APIs can you host yourself?
MirrorFly sells a one-time license by quote that you host, with source code as an option and a demo call in place of a free trial. QuickBlox offers on-premise hosting too, and TalkJS sells on-premise and private cloud installs as an Enterprise add-on.
What do chat APIs cost at 10,000 and 25,000 users?
Each price is the cheapest self-serve plan with chat that covers that many monthly active users, billed annually where the vendor offers it.
| Vendor | 10,000 users | 25,000 users | Chat UI | Message history on that plan |
|---|---|---|---|---|
| TalkJS | $239 (Basic) | $499 (Growth) | Inbox, chatbox and popup | Every message, on every plan |
| CometChat | $299 (Basic) | $699 (Basic) | UI kits | 6 months, longer at extra cost |
| Stream | $399 (Start) | $1,049 (Start, its cheapest plan that covers 25,000: 27,000 users) | UI SDKs | Up to a stored-message limit (5 million on Start at 10,000 users) |
| Sendbird | $429 (Starter) | $1,119 (Starter) | UIKits | 6 months |
| PubNub | About $550 (its estimate) | About $1,130 (its estimate) | None (headless) | Unlimited on Pro |
| Twilio Conversations | About $466 to $478, pay as you go | By quote (above 20,000 users) | None | Not listed |
| QuickBlox | $107 (Starter, 10,000 registered users) | $269 (Growth, 25,000 registered users) | UI kits | 3 months (Starter), 6 months (Growth) |
- QuickBlox counts registered users, everyone who has ever signed up, so its tiers fill with people who no longer use your app. The other prices count monthly active users.
- Twilio's range is our arithmetic from its published per-user rates: the first 200 users free, $0.05 each up to 5,000 and $0.0475 each up to 10,000. Twilio doesn't say whether the tiers are graduated, so the low end prices every paid user at the $0.0475 rate.
- Extra users: each 1,000 users over your plan's limit costs $40 on TalkJS Basic and $30 on Growth, $90 on Stream Start at 10,000 and $100 on CometChat Basic. Sendbird says overages may apply and publishes no rate.
- Users online at once: the Stream plan at 10,000 users includes 500 concurrent connections, then $0.99 each. Sendbird and CometChat include concurrent connections for 5% of your monthly active users. TalkJS has no hard limit, with fair use of about 10%.
- Ably bills $2.50 per million messages and $1.00 per million connection and channel minutes, plus a base fee ($29 on Standard, $399 on Pro), so a busy group chat costs more than the same users in one-on-one chats.
- On TalkJS, message search and real-time translation come with Growth.
What's left if you build chat yourself?
A WebSocket library gets messages from one browser to another. Everything the APIs above handle for you is still yours to build: delivery to users who were offline, notifications, history, moderation and the screens. Socket.IO, for example, delivers each event at most once by default. Events a disconnected client missed aren't sent when it reconnects, and its docs say additional guarantees "must be implemented in your application".
An AI coding agent writes that code faster, but it's still your code to run and fix. If you build with one, point it at talkjs.com/SKILL.md and it adds TalkJS to your app instead.
Is there a free chat API?
For building and testing, yes. TalkJS development mode is free, includes every feature and has no time limit. There's no free production plan: you pay when you go live.
- Stream's Build plan is free up to 1,000 monthly active users.
- Sendbird offers a free trial up to 1,000 monthly active users.
- CometChat's Build plan is free for development, up to 100 users.
- PubNub's Free plan covers up to 200 monthly active users, for building and testing.