# Alchemy Webhooks

## When to Use This Skill

* How do I receive Alchemy webhooks?
* How do I verify Alchemy webhook signatures (the `X-Alchemy-Signature` header)?
* How do I handle ADDRESS_ACTIVITY, MINED_TRANSACTION, or NFT_ACTIVITY events?
* Why is my Alchemy webhook signature verification failing?
* How do I set up Alchemy Notify webhooks for onchain activity?

## Verification (core)

Alchemy signs every webhook with HMAC-SHA256 over the raw request body, hex-encoded, in the
`X-Alchemy-Signature` header. There is no `sha256=` prefix and no timestamp — just the hex digest.
The key is the per-webhook signing key (copied from the top-right of that webhook's detail page in
the Notify dashboard, or fetched via the Notify API), not your app's Auth Token.

The `alchemy-sdk` npm package manages webhook CRUD but does not verify signatures — implement HMAC
yourself. Always compute the HMAC over the raw body; a re-serialized JSON body will not match.

```javascript
const crypto = require('crypto');

function verifyAlchemySignature(rawBody, signature, signingKey) {
  if (!signature) return false;
  const digest = crypto
    .createHmac('sha256', signingKey)
    .update(rawBody, 'utf8')   // rawBody: exact bytes/string received, never re-stringified JSON
    .digest('hex');
  try {
    return crypto.timingSafeEqual(Buffer.from(signature), Buffer.from(digest));
  } catch {
    return false; // length mismatch = invalid
  }
}

```

> For complete handlers with route wiring, event dispatch, and tests, see:
> 
> * [examples/express/](https://github.com/hookdeck/webhook-skills/tree/main/skills/alchemy-webhooks/examples/express/)
> * [examples/nextjs/](https://github.com/hookdeck/webhook-skills/tree/main/skills/alchemy-webhooks/examples/nextjs/)
> * [examples/fastapi/](https://github.com/hookdeck/webhook-skills/tree/main/skills/alchemy-webhooks/examples/fastapi/)

## Common Event Types

The webhook `type` field identifies the event. Alchemy webhooks are scoped per chain/network.

| Type | Triggered When |
| --- | --- |
| `ADDRESS_ACTIVITY` | ETH/ERC-20/ERC-721/ERC-1155 transfers involving tracked addresses |
| `MINED_TRANSACTION` | A tracked transaction is mined into a block |
| `DROPPED_TRANSACTION` | A tracked transaction is dropped from the mempool |
| `NFT_ACTIVITY` | ERC-721/ERC-1155 transfers for tracked NFT contracts |
| `NFT_METADATA_UPDATE` | Metadata for a tracked NFT is refreshed |
| `GRAPHQL` | A Custom Webhook GraphQL query matches new onchain data |

> For full event and payload reference, see [references/overview.md](https://github.com/hookdeck/webhook-skills/blob/main/skills/alchemy-webhooks/references/overview.md) and the
> [Alchemy Webhooks docs](https://www.alchemy.com/docs/reference/webhooks-overview).

## Environment Variables

```bash
ALCHEMY_SIGNING_KEY=whsec_or_your_per_webhook_signing_key   # top-right of the webhook's detail page
# Only needed for programmatic webhook CRUD via the Notify API / alchemy-sdk:
ALCHEMY_AUTH_TOKEN=your_app_auth_token                      # distinct from the signing key

```

## Local Development

```bash
# Start tunnel (no account needed)
npx hookdeck-cli listen 3000 alchemy --path /webhooks/alchemy

```

Configure the resulting URL as the webhook target in the Alchemy Notify dashboard. Optionally
allowlist Alchemy's egress IPs: `54.236.136.17` and `34.237.24.169`.

## Reference Materials

* [references/overview.md](https://github.com/hookdeck/webhook-skills/blob/main/skills/alchemy-webhooks/references/overview.md) - Alchemy webhook types, payloads, common events
* [references/setup.md](https://github.com/hookdeck/webhook-skills/blob/main/skills/alchemy-webhooks/references/setup.md) - Dashboard + Notify API / alchemy-sdk configuration
* [references/verification.md](https://github.com/hookdeck/webhook-skills/blob/main/skills/alchemy-webhooks/references/verification.md) - Signature verification details and gotchas