# Chat Messaging
Stream Chat adds real-time messaging to your app: direct messages, group conversations, livestream chat and support flows. The API keeps channels, messages, threads, reactions and read state in sync across devices; the SDKs add offline storage and prebuilt UI on every major platform.
See it running in the [live demos](https://getstream.io/chat/demos/messaging/), or take the [interactive tour](https://getstream.io/chat/tour/) of the API.
## How the pieces fit together
Your app talks to the Stream API through a client SDK, with prebuilt UI components on top where you want them. A server-side SDK on your backend signs the [user tokens](https://getstream.io/docs/platform/authentication/) clients connect with and handles the tasks that need your API secret.
```mermaid
flowchart LR
subgraph app[Your app]
ui[UI components] --> client[Chat client SDK]
end
subgraph backend[Your backend]
server[Server-side SDK]
end
client <--> api[Stream API]
server --> api
server -. user token .-> client
```
## SDKs
Chat ships in three tiers. Start with the UI components and drop down a tier where you need more control.
### UI Components
Complete chat interfaces with message lists, channel lists, threads and reactions built in.
### Client Side SDKs
Connection handling, channel state and offline support, with the interface left to you.
### Server Side SDKs
Full API access from your backend: provision users, create channels, send messages and enforce moderation.
## Build with AI
Your AI agent can work with Stream from the terminal with the [Stream CLI](https://getstream.io/cli/docs/). There's also an [Agent Skills](https://getstream.io/agent-skills/docs/) pack so it can look up docs and configure your app.
```bash
curl -fsSL https://getstream.io/cli.sh | bash
getstream skills
```
## Platform
Users, auth and the rest of the account-level machinery work the same in every Stream product, so they are documented once in the [platform docs](https://getstream.io/docs/platform/). Chat apps touch these first:
## Start here
Each tutorial builds a working chat app from an empty project. Pick your platform:
## FAQ
**Which SDK do I need?**
Start with a UI component SDK. Use a client SDK to build your own interface on the same state layer, and a server-side SDK for anything that touches your API secret.
**Does chat work offline?**
Yes. The client SDKs store messages locally and update the UI optimistically, then sync when the connection returns.
**Do I need my own backend?**
In production, yes: user tokens are [signed with your API secret](https://getstream.io/docs/platform/authentication/) on your server. For a prototype, [developer tokens](https://getstream.io/docs/platform/authentication/#developer-tokens) let clients connect without one.
**Does Chat include moderation?**
[Stream Moderation](https://getstream.io/moderation/docs/) plugs into Chat: AI engines screen messages and borderline cases go to a human review queue.
**Do Chat and Video share users?**
Yes. Users, tokens and roles are app-level and shared by every Stream product; the [platform docs](https://getstream.io/docs/platform/) cover them once.
**Can I read these docs as markdown?**
Append `.md` to any page URL. [/llms.txt](https://getstream.io/llms.txt) indexes every page.
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This page was last updated at 2026-09-08T17:14:05.034Z.
For the most recent version of this documentation, visit [https://getstream.io/chat/docs/](https://getstream.io/chat/docs/).