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For this guide, we’ll go over:

Setting up Sign-in with neynar

Building the user feed

Building channels feed

Building user profiles

Before we begin, you can access the complete source code for this guide on GitHub. Let’s get started!

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Creating the app

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Setting up the project

Create a new next.js app using the following command: 
npx create-next-app app-name
You can choose the configuration based on your personal preference, I am using this config for the guide:
Create Next.js app
Once the app is created, install the packages that we are going to need for the command: 
npm i @neynar/react @neynar/nodejs-sdk
Once the dependencies are installed you can open it in your favourite and we can start working on the client!

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Setting up Sign-in with neynar

Head over to the layout.tsx file and wrap your app in a NeynarContextProvider like this: 
"use client";

import "./globals.css";
import { NeynarContextProvider, Theme } from "@neynar/react";
import "@neynar/react/dist/style.css";

export default function RootLayout({
  children,
}: Readonly<{
  children: React.ReactNode;
}>) {
  return (
    <html lang="en">
      <NeynarContextProvider
        settings={{
          clientId: process.env.NEXT_PUBLIC_NEYNAR_CLIENT_ID || "",
          defaultTheme: Theme.Dark,
          eventsCallbacks: {
            onAuthSuccess: () => {},
            onSignout() {},
          },
        }}
      >
        <body>{children}</body>
      </NeynarContextProvider>
    </html>
  );
}
We are passing some settings here like clientId, defaultTheme and eventsCallbacks.
  • clientId: This is going to be the client ID you get from your neynar, add it to your .env.local file as NEXT_PUBLIC_NEYNAR_CLIENT_ID.
Neynar client ID

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Make sure to add localhost to the authorized origins

  • defaultTheme: default theme lets you change the theme of your sign-in button, currently, we have only light mode but dark mode is going to be live soon.
  • eventsCallbacks: This allows you to perform certain actions when the user signs out or auth is successful.
I’ve also added a styles import from the neynar react package here which is needed for the styles of the sign-in button. Now, let’s create a header component where we can add the sign-in with Neynar button. So, create a new components/Header.tsx file and add the following: 
"use client";

import { NeynarAuthButton } from "@neynar/react";
import Link from "next/link";

export const Header: FC = () => {
  return (
    <div className="flex items-center justify-between px-16 pt-4 text-white">
              <Link href="/" className="text-3xl" style={{fontWeight: 500}}>
        FarCaster App
      </Link>

      <NeynarAuthButton className="right-4 top-4" />
    </div>
  );
};
We’ll add the header to the layout.tsx file since we are going to need it on all the pages: 
"use client";

import "./globals.css";
import { NeynarContextProvider, Theme } from "@neynar/react";
import "@neynar/react/dist/style.css";
import { Header } from "@/components/Header";

export default function RootLayout({
  children,
}: Readonly<{
  children: React.ReactNode;
}>) {
  return (
    <html lang="en">
      <NeynarContextProvider
        settings={{
          clientId: process.env.NEXT_PUBLIC_NEYNAR_CLIENT_ID || "",
          defaultTheme: Theme.Dark,
          eventsCallbacks: {
            onAuthSuccess: () => {},
            onSignout() {},
          },
        }}
      >
        <body>
          <Header />
          {children}
        </body>
      </NeynarContextProvider>
    </html>
  );
}
If you head over to your app you’ll be able to see a sign-in button on the screen. Go ahead and try signing in!
Sign-in button
Now that our sign-in button is working let’s start working on showing the feed!

​
Building the feed

In the page.tsx file add the following: 
"use client";

import { NeynarFeedList, useNeynarContext } from "@neynar/react";

export default function Home() {
  const { user } = useNeynarContext();

  return (
    <main className="flex min-h-screen p-16">
      <div className="ml-40 flex flex-col gap-6">
        <NeynarFeedList
          feedType={user?.fid ? "following" : "filter"}
          fid={user?.fid}
          filterType="global_trending"
        />
      </div>
    </main>
  );
}
Here, we are using the NeynarFeedList component to show the trending casts if the user is not signed in, but, if they are signed in we show the following feed based on their fid.
Feed
Now, let’s also show the list of channels that the user is following.

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Building the channels list and channel feed

To get the list of channels that a user is following we’ll use the neynar APIs. So, let’s first initialise the client in a new lib/neynarClient.ts file like this: 
import { NeynarAPIClient } from "@neynar/nodejs-sdk";

const neynarClient = new NeynarAPIClient(process.env.NEYNAR_API_KEY!);

export default neynarClient;

​
Make sure to add the NEYNAR_API_KEY to your .env file.

Then, create a new file api/channels/route.ts in the app directory and add the following: 
import neynarClient from "@/lib/neynarClient";
import { NextResponse } from "next/server";

export const GET = async (req: Request) => {
  try {
    const { searchParams } = new URL(req.url);
    const fid = searchParams.get("fid");

    const channels = await neynarClient.fetchUserChannels(Number(fid));

    return NextResponse.json(channels, { status: 200 });
  } catch (error) {
    return NextResponse.json(
      { error: (error as any).response?.data?.message },
      { status: (error as any).response?.status || 500 }
    );
  }
};
This will fetch the channels a user is following using the neynarClient and return it. Let’s now use it on the home page. Head back to the page.tsx file and add the following: 
"use client";

import { Channel } from "@neynar/nodejs-sdk/build/neynar-api/v2";
import { NeynarFeedList, useNeynarContext } from "@neynar/react";
import Link from "next/link";
import { useEffect, useState } from "react";

export default function Home() {
  const { user } = useNeynarContext();
  const [channels, setChannels] = useState<any | null>();

  const fetchChannels = async () => {
    if (!user) {
      return;
    }

    const response = await fetch(`/api/channels?fid=${user?.fid}`);
    const data = await response.json();
    setChannels(data);
  };

  useEffect(() => {
    if (user) {
      fetchChannels();
    }
  }, [user]);

  return (
    <main className="flex min-h-screen p-16">
      {user && (
        <div className="flex flex-col">
          <h1 className="text-3xl" style={{fontWeight: 500}}>Channels</h1>
          <div className="flex flex-col">
            {channels &&
              channels.channels.map((channel: Channel) => (
                <div key={channel.url} className="rounded-lg p-4">
                  <Link href={`/channel/${channel.id}`}>{channel.name}</Link>
                </div>
              ))}
          </div>
        </div>
      )}

      <div className="ml-40 flex flex-col gap-6">
        <NeynarFeedList
          feedType={user?.fid ? "following" : "filter"}
          fid={user?.fid}
          filterType="global_trending"
        />
      </div>
    </main>
  );
}
Here, we are now fetching the list of channels that the user follows and creating links with the name of the channel. These link to another page which we are yet to build but you should be able to see the list of channels now!
Channels
Now, let’s build out the channel page as well which will show the feed of a specific channel. Create a new channel/[channelId]/page.tsx file in the app folder and add the following: 
import { NeynarFeedList } from "@/components/Neynar";

export default async function Page({
  params: { channelId },
}: {
  params: { channelId: string };
}) {
  return (
    <main className="mt-4 flex min-h-screen w-full flex-col items-center justify-between p-24">
      <h1 className="text-3xl mb-4" style={{fontWeight: 500}}>{channelId}</h1>
      <NeynarFeedList
        feedType="filter"
        channelId={channelId}
        viewerFid={2}
        limit={50}
        filterType="channel_id"
      />
    </main>
  );
}
Here, you can see that we are importing the component from a @/components/Neynar file and not the package directly because it is a client component. So, create a new components/Neynar.tsx file and add the following: 
"use client";

import { NeynarProfileCard, NeynarFeedList } from "@neynar/react";

export { NeynarProfileCard, NeynarFeedList };
This will filter the feed based on the channelId and show only the casts made in that channel. If you go ahead and click on one of the channels you’ll be able to see something like this:
Channel

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Building user profiles

Let’s also build a profile page for every user which shows their profile card and the casts they have created. Create a new file profile/[username]/page.tsx in the app folder and add the following: 
import { NeynarProfileCard, NeynarFeedList } from "@/components/Neynar";
import neynarClient from "@/lib/neynarClient";

async function getData(username: string) {
  const user = await neynarClient.lookupUserByUsername(username);

  return { user: user.result.user };
}

export default async function Page({
  params: { username },
}: {
  params: { username: string };
}) {
  const { user } = await getData(username);

  return (
    <main className="flex min-h-screen w-full flex-col items-center justify-between p-24">
      <NeynarProfileCard fid={user.fid} />
      <div className="mt-4 flex items-center">
        <NeynarFeedList
          feedType="filter"
          fid={user.fid}
          fids={`${user.fid}`}
          withRecasts={false}
          limit={50}
        />
      </div>
    </main>
  );
}
Here, I am first resolving the username in the path to get the user object which can be later used to get the fid of the user. Then, we are displaying the ProfileCard and the FeedList filtered based on the user’s fid. If you go to /profile/username then you’ll be able to see the user’s profile!
Profile

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Conclusion

In this tutorial, we successfully built a Farcaster client with Next.js and the Neynar React SDK. Along the way, we covered essential features such as user authentication, creating feeds, fetching channels, and building user profiles. These steps give you a solid foundation to further enhance your client by adding more advanced features or customizing it to meet your specific needs. To explore the full implementation, visit the GitHub repository. If you have any questions or want to share your progress, reach out to us on warpcast or Slack.