Neynar Documentation

If you want to integrate Farcaster auth for your users, easiest way to start is Sign in with Neynar (Neynar pays all onchain fee)
If you want dedicated signers for your user or bot, simplest to clone this example app for quickstart

This guide demonstrates adding an Ethereum address verification with the Neynar SDK. Check out this Getting Started Guide to learn how to set up your environment and get an API key. First, initialize the client:

// npm i @neynar/nodejs-sdk
import { NeynarAPIClient, Configuration } from "@neynar/nodejs-sdk";

// make sure to set your NEYNAR_API_KEY .env
// don't have an API key yet? get one at neynar.com
const config = new Configuration({
  apiKey:process.env.NEYNAR_API_KEY,
});

const client = new NeynarAPIClient(config);
const signer = process.env.NEYNAR_SIGNER;

Then like a cast:

const hash = "0x6932a9256f34e18892d498abb6d00ccf9f1c50d6";
client.publishReaction({ signerUuid: signer, reactionType: "like", target:hash });

Recasting works the same way, just replace “like” with “recast”:

const hash = "0x6932a9256f34e18892d498abb6d00ccf9f1c50d6";
client.publishReaction({ signerUuid: signer, reactionType: "like", target:hash });

The end result should look like this:

{
  success: true;
}

To verify that the reaction was published, you can fetch the cast’s reactions:

const types = ReactionsType.All;
const reactions = await client.fetchCastReactions({ hash, types: [types] });
console.log(reactions);

Which would print out

{
  "result": {
    "casts": [
      {
        "type": "like",
        "hash": "0x691fabb3fc58bd4022d4358b2bc4f44469ad959a",
        "reactor": {
          "fid": "4640",
          "username": "picture",
          "displayName": "Picture",
          "pfp": {
            "url": "https://lh3.googleusercontent.com/erYudyT5dg9E_esk8I1kqB4bUJjWAmlNu4VRnv9iUuq_by7QjoDtZzj_mjPqel4NYQnvqYr1R54m9Oxp9moHQkierpY8KcYLxyIJ"
          },
          "followerCount": "45",
          "followingCount": "57"
        },
        "timestamp": "2023-12-10T15:26:45.000Z",
        "castHash": "0x6932a9256f34e18892d498abb6d00ccf9f1c50d6"
      }
    ],
    "next": {
      "cursor": null
    }
  }
}

That’s it! You can now like or recast any cast on Farcaster. PS - to learn more about how writes technically work on Farcaster, read Write to Farcaster with Neynar Managed Signers

Ready to start building?

Get your subscription at neynar.com and reach out to us on Slack with any questions!

Get Started

Build Bots and Agents

Build Farcaster Mini Apps

Fetch User Information

Fetch Cast Information

Fetch Farcaster Feeds

Onboard New Users

Write Data to Farcaster

Filter Spam, Low Quality Data

Host Farcaster Mini Apps

Run Queries on FC Data

Render Farcaster in React

Get Events Via Webhooks

Fetch Notifications

Create Onchain Transactions

Intersect Onchain & Social Data

Write Direct Casts

Get Farcaster Storage Data

Publish Actions on FC Apps

Get Farcaster Data on Base

Explore Network Health

Get Hypersub Subscriptions

Contribute To Development

Add a Verification

Ready to start building?

​Ready to start building?

Ready to start building?