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  • Package: @cometchat/chat-uikit-react
  • Framework: React Router
  • Key components: CometChatConversations + CometChatMessageList
  • Required setup: CometChatUIKit.init(UIKitSettings) then CometChatUIKit.login("UID")
  • Parent guide: React Router Integration
The Conversation List + Message View layout offers a seamless two-panel chat interface, commonly used in modern messaging applications like WhatsApp Web, Slack, and Microsoft Teams. This design enables users to switch between conversations effortlessly while keeping the chat window open, ensuring a smooth, real-time messaging experience.

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User Interface Overview

This layout is structured into three key sections:
  1. Sidebar (Conversation List) – Displays active conversations, including users and groups.
  2. Message View – Shows chat messages for the selected conversation in real-time.
  3. Message Composer – Provides an input field for typing and sending messages, along with support for media, emojis, and reactions.

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Step-by-Step Guide

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Step 1: Create Sidebar

Let’s create the Sidebar component which will render different conversations.

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Folder Structure

Create a CometChatSelector folder inside your src/app directory and add the following files: 
src/app/
│── CometChatSelector/
│   ├── CometChatSelector.tsx
│   ├── CometChatSelector.css

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Download the Icon

These icons are available in the CometChat UI Kit assets folder. You can find them at:
🔗 GitHub Assets Folder
CometChatSelector.tsx
import { useEffect, useState } from "react";
import { Conversation, Group, User } from "@cometchat/chat-sdk-javascript";
import { CometChatConversations, CometChatUIKitLoginListener } from "@cometchat/chat-uikit-react";
import { CometChat } from '@cometchat/chat-sdk-javascript';
import "./CometChatSelector.css";

// Define props interface for component
interface SelectorProps {
    onSelectorItemClicked?: (input: User | Group | Conversation, type: string) => void;
}

// CometChatSelector component definition
export const CometChatSelector = (props: SelectorProps) => {
    const {
        onSelectorItemClicked = () => { }, // Default function if no prop is provided
    } = props;

    // State to store the currently logged-in user
    const [loggedInUser, setLoggedInUser] = useState<CometChat.User | null>();
    
    // State to track the currently selected item (conversation, user, group, or call)
    const [activeItem, setActiveItem] = useState<
        CometChat.Conversation | CometChat.User | CometChat.Group | CometChat.Call | undefined
    >();

    useEffect(() => {
        // Retrieve the logged-in user from CometChat's login listener
        let loggedInUser = CometChatUIKitLoginListener.getLoggedInUser();
        setLoggedInUser(loggedInUser);
    }, [CometChatUIKitLoginListener?.getLoggedInUser()]); // Dependency array to trigger effect when user changes

    return (
        <>
            {/* Render CometChatConversations only if a user is logged in */}
            {loggedInUser && (
                <>
                    <CometChatConversations
                        activeConversation={activeItem instanceof CometChat.Conversation ? activeItem : undefined}
                        onItemClick={(e) => {
                            setActiveItem(e); // Update the selected item state
                            onSelectorItemClicked(e, "updateSelectedItem"); // Trigger callback with selected item
                        }}
                    />
                </>
            )}
        </>
    );
};

​
Step 2: Render Experience

Now we will create the CometChatNoSSR.tsx & CometChatNoSSR.css files. Here, we will initialize the CometChat UI Kit, log in a user, and build the messaging experience using CometChatMessageHeader, CometChatMessageList, and CometChatMessageComposer components. 
src/app/
│── CometChatNoSSR/
│   ├── CometChatNoSSR.tsx
│   ├── CometChatNoSSR.css
CometChatNoSSR.tsx
import React, { useEffect, useState } from "react";
import {
  CometChatMessageComposer,
  CometChatMessageHeader,
  CometChatMessageList,
  CometChatUIKit,
  UIKitSettingsBuilder
} from "@cometchat/chat-uikit-react";
import { CometChat } from "@cometchat/chat-sdk-javascript";
import { CometChatSelector } from "../CometChatSelector/CometChatSelector";
import "./CometChatNoSSR.css";

const COMETCHAT_CONSTANTS = {
  APP_ID: "",
  REGION: "",
  AUTH_KEY: "",
};

const CometChatNoSSR: React.FC = () => {
  const [initialized, setInitialized] = useState(false);
  const [user, setUser] = useState<CometChat.User | null>(null);
  const [selectedUser, setSelectedUser] = useState<CometChat.User>();
  const [selectedGroup, setSelectedGroup] = useState<CometChat.Group>();

  useEffect(() => {
    if (typeof window === 'undefined') return;

    const UIKitSettings = new UIKitSettingsBuilder()
      .setAppId(COMETCHAT_CONSTANTS.APP_ID)
      .setRegion(COMETCHAT_CONSTANTS.REGION)
      .setAuthKey(COMETCHAT_CONSTANTS.AUTH_KEY)
      .subscribePresenceForAllUsers()
      .build();

    CometChatUIKit.init(UIKitSettings)
      ?.then(() => {
        console.log("Initialization completed successfully");
        setInitialized(true);

        CometChatUIKit.getLoggedinUser().then((loggedInUser) => {
          if (!loggedInUser) {
            CometChatUIKit.login("cometchat-uid-1") //TODO: Replace with dynamic UID
              .then((u) => {
                console.log("Login Successful", { u });
                setUser(u);
              })
              .catch((error) => console.error("Login failed", error));
          } else {
            console.log("Already logged-in", { loggedInUser });
            setUser(loggedInUser);
          }
        });
      })
      .catch((error) => console.error("Initialization failed", error));
  }, []);

  if (!initialized || !user) {
    return <div>Initializing Chat...</div>;
  }

  return (
    <div className="conversations-with-messages">
      <div className="conversations-wrapper">
        <CometChatSelector
          onSelectorItemClicked={(activeItem) => {
            let item = activeItem;
            if (activeItem instanceof CometChat.Conversation) {
              item = activeItem.getConversationWith();
            }

            if (item instanceof CometChat.User) {
              setSelectedUser(item);
              setSelectedGroup(undefined);
            } else if (item instanceof CometChat.Group) {
              setSelectedUser(undefined);
              setSelectedGroup(item);
            } else {
              setSelectedUser(undefined);
              setSelectedGroup(undefined);
            }
          }}
        />
      </div>

      {selectedUser || selectedGroup ? (
        <div className="messages-wrapper">
          <CometChatMessageHeader user={selectedUser} group={selectedGroup} />
          <CometChatMessageList user={selectedUser} group={selectedGroup} />
          <CometChatMessageComposer user={selectedUser} group={selectedGroup} />
        </div>
      ) : (
        <div className="empty-conversation">Select Conversation to start</div>
      )}
    </div>
  );
};

export default CometChatNoSSR;

​
Step 3: Disable SSR and Render the CometChat Component

Create a file CometChat.tsx inside the routes folder: 
import React, { lazy, Suspense, useEffect, useState } from "react";
import "@cometchat/chat-uikit-react/css-variables.css";

// Lazy import to prevent SSR crash
const CometChatNoSSR = lazy(() => import("../CometChatNoSSR/CometChatNoSSR"));

export default function CometChatRoute() {
  const [mounted, setMounted] = useState(false);

  useEffect(() => {
    setMounted(true);
  }, []);

  return mounted ? (
    <Suspense fallback={<div>Loading...</div>}>
      <CometChatNoSSR />
    </Suspense>
  ) : (
    <div>Loading...</div>
  );
}
Now, create a route for CometChat in your routes file: 
import { type RouteConfig, index, route } from "@react-router/dev/routes";

export default [
  index("routes/home.tsx"),
  route("chat", "routes/CometChat.tsx"), // Chat Route
] satisfies RouteConfig;
Why disable SSR? CometChat UI Kit Builder relies on browser APIs such as window, document, and WebSockets. Since React Router renders on the server by default, disabling SSR for this component prevents runtime errors.

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Step 4: Update App CSS

Next, add the following styles to app.css to ensure CometChat UI Kit is properly styled.
app.css
:root {
  --background: #ffffff;
  --foreground: #171717;
}

@media (prefers-color-scheme: dark) {
  :root {
    --background: #0a0a0a;
    --foreground: #ededed;
  }
}

/** Give your App a height of `100%`. Keep other CSS properties in the below selector as it is. */
.root {
  height: 100%;
}

html,
body {
  height: 100%;
}

html,
body {
  max-width: 100vw;
  overflow-x: hidden;
}

body {
  color: var(--foreground);
  background: var(--background);
  font-family: Arial, Helvetica, sans-serif;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
}

* {
  box-sizing: border-box;
  padding: 0;
  margin: 0;
}

a {
  color: inherit;
  text-decoration: none;
}

@media (prefers-color-scheme: dark) {
  html {
    color-scheme: dark;
  }
}

​
Step 5: Run Your Application

  1. Start the development server 
    npm run dev
  2. Verify the chat interface
  • In your browser, navigate to the /chat route (e.g., http://localhost:3000/chat).
  • Confirm that the chat experience loads as expected.

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Common Failure Modes

SymptomCauseFix
Component doesn’t renderCometChatUIKit.init() not called or not awaitedEnsure init completes before rendering. See Methods
Component renders but shows no dataUser not logged inCall CometChatUIKit.login("UID") after init
CSS/theme not appliedMissing CSS importAdd @import url("@cometchat/chat-uikit-react/css-variables.css"); in your CSS
Blank screen after loginComponent mounted before init/login completesUse state to conditionally render after login resolves
Messages not loadingInvalid user/group object passedEnsure you fetch the user/group via SDK before passing to components

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Next Steps

Advanced Customizations

Personalize the chat UI to align with your brand.

Components Overview

Explore all available prebuilt UI components.

React Router Integration

Return to the React Router setup guide.

Core Features

Learn about messaging, real-time updates, and more.