# Overview

## Introduction

Chat21 is a multi platform SDK that adds Instant Messaging to your iOS, Android and Web applications.

IOS and Android SDKs provide you methods to initialize and configure chat features embedded in your own mobile app. Chat21 SDKs helps you to build a standalone chat application as well. The SDKs provide ready to use UI components and *extension points* for embedding and customizing a chat into your app. Chat21 uses [Firebase](http://firebase.google.com) platform as backend.

Please choose a platform to start:

## iOS

[Get started tutorial](https://docs.chat21.org/ios/get-started)

[APIs](https://github.com/chat21/chat21-docs/tree/8ab923d159962acfcaf604579422dfbfd81c7689/ios/api/README.md)

## Android

[Get started tutorial](https://docs.chat21.org/android/get-started-for-android)


---

# Agent Instructions: Querying This Documentation

If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question.

Perform an HTTP GET request on the current page URL with the `ask` query parameter:

```
GET https://docs.chat21.org/master.md?ask=<question>
```

The question should be specific, self-contained, and written in natural language.
The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.

Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.