Alchemy Webhooks & Events (Notify API)

Overview

Alchemy Notify provides real-time push notifications for on-chain events. Instead of polling, receive webhook callbacks for wallet activity, mined transactions, dropped transactions, and smart contract events.

Webhook Types

Type	Trigger	Use Case
Address Activity	ETH/token transfer to/from address	Wallet notifications
Mined Transaction	Transaction confirmed on-chain	Payment confirmation
Dropped Transaction	Transaction removed from mempool	Failed tx alerting
NFT Activity	NFT transfer events	Marketplace notifications
Custom Webhook	GraphQL-defined filter	Complex event tracking

Instructions

Step 1: Create Webhook via Dashboard or API

# Create Address Activity webhook via Alchemy API
curl -X POST "https://dashboard.alchemy.com/api/create-webhook" \
  -H "X-Alchemy-Token: ${ALCHEMY_AUTH_TOKEN}" \
  -H "Content-Type: application/json" \
  -d '{
    "network": "ETH_MAINNET",
    "webhook_type": "ADDRESS_ACTIVITY",
    "webhook_url": "https://your-app.com/webhooks/alchemy",
    "addresses": [
      "0xd8dA6BF26964aF9D7eEd9e03E53415D37aA96045"
    ]
  }'

Step 2: Webhook Handler with Signature Verification

// src/webhooks/alchemy-handler.ts
import express from 'express';
import crypto from 'crypto';

const router = express.Router();

router.post('/webhooks/alchemy',
  express.raw({ type: 'application/json' }),
  async (req, res) => {
    // Verify webhook signature
    const signature = req.headers['x-alchemy-signature'] as string;
    if (!verifySignature(req.body.toString(), signature)) {
      return res.status(401).json({ error: 'Invalid signature' });
    }

    const event = JSON.parse(req.body.toString());
    await processAlchemyEvent(event);
    res.status(200).json({ ok: true });
  }
);

function verifySignature(body: string, signature: string): boolean {
  const signingKey = process.env.ALCHEMY_WEBHOOK_SIGNING_KEY!;
  const hmac = crypto.createHmac('sha256', signingKey);
  hmac.update(body, 'utf8');
  const digest = hmac.digest('hex');
  return crypto.timingSafeEqual(Buffer.from(signature), Buffer.from(digest));
}

Step 3: Event Router

// src/webhooks/event-router.ts
interface AlchemyWebhookEvent {
  webhookId: string;
  id: string;
  createdAt: string;
  type: 'ADDRESS_ACTIVITY' | 'MINED_TRANSACTION' | 'DROPPED_TRANSACTION' | 'NFT_ACTIVITY';
  event: {
    network: string;
    activity: Array<{
      fromAddress: string;
      toAddress: string;
      value: number;
      asset: string;
      category: 'external' | 'internal' | 'erc20' | 'erc721' | 'erc1155';
      hash: string;
      blockNum: string;
    }>;
  };
}

async function processAlchemyEvent(event: AlchemyWebhookEvent): Promise<void> {
  switch (event.type) {
    case 'ADDRESS_ACTIVITY':
      for (const activity of event.event.activity) {
        console.log(`${activity.category} transfer: ${activity.value} ${activity.asset}`);
        console.log(`  From: ${activity.fromAddress}`);
        console.log(`  To: ${activity.toAddress}`);
        console.log(`  Tx: ${activity.hash}`);
        // Trigger application logic (e.g., update balance, send notification)
      }
      break;

    case 'MINED_TRANSACTION':
      console.log('Transaction mined:', event.event);
      break;

    case 'DROPPED_TRANSACTION':
      console.log('Transaction dropped:', event.event);
      // Alert user their transaction was dropped
      break;

    case 'NFT_ACTIVITY':
      for (const activity of event.event.activity) {
        console.log(`NFT transfer: ${activity.asset} #${activity.value}`);
      }
      break;
  }
}

Step 4: Programmatic Webhook Management

// src/webhooks/manage-webhooks.ts
import { Alchemy, Network, WebhookType } from 'alchemy-sdk';

const alchemy = new Alchemy({
  apiKey: process.env.ALCHEMY_API_KEY,
  network: Network.ETH_MAINNET,
  authToken: process.env.ALCHEMY_AUTH_TOKEN, // Required for Notify API
});

async function setupAddressWebhook(addresses: string[], webhookUrl: string) {
  const webhook = await alchemy.notify.createWebhook(
    webhookUrl,
    WebhookType.ADDRESS_ACTIVITY,
    { addresses, network: Network.ETH_MAINNET }
  );
  console.log(`Webhook created: ${webhook.id}`);
  return webhook;
}

async function listWebhooks() {
  const webhooks = await alchemy.notify.getAllWebhooks();
  for (const wh of webhooks.webhooks) {
    console.log(`${wh.id}: ${wh.webhookType} → ${wh.webhookUrl} (${wh.isActive ? 'active' : 'inactive'})`);
  }
}

async function addAddressToWebhook(webhookId: string, newAddresses: string[]) {
  await alchemy.notify.updateWebhook(webhookId, {
    addAddresses: newAddresses,
  });
}

Output

• Address Activity webhook for wallet monitoring
• HMAC signature verification for webhook security
• Event router handling all Alchemy webhook types
• Programmatic webhook management via Notify API

Error Handling

Issue	Cause	Solution
Invalid signature	Wrong signing key	Copy from Alchemy webhook details page
Missing events	Webhook URL not reachable	Ensure HTTPS endpoint is publicly accessible
Duplicate events	No idempotency	Track webhook event IDs

Resources

• Alchemy Webhooks Overview
• Alchemy Webhook Types
• Alchemy Notify Tutorial

Next Steps

For performance optimization, see alchemy-performance-tuning.