# FastSpring Webhooks

## When to Use This Skill

* Setting up FastSpring webhook handlers
* How do I verify FastSpring webhook signatures?
* Why is my `X-FS-Signature` verification failing?
* Handling `order.completed`, `subscription.activated`, or `subscription.charge.completed` events
* Iterating the batched `events` array FastSpring delivers in each POST

## Verification (core)

FastSpring signs the exact raw request body with HMAC-SHA256 keyed on your
per-webhook HMAC SHA256 Secret, base64-encodes the digest, and sends it in the
`X-FS-Signature` header. Pass the raw body (do not parse/re-serialize first),
recompute, and compare timing-safe. Each POST batches multiple events in an
`events` array — verify the signature once against the whole body, then iterate.

> Note: Signing is only active when the HMAC secret is set on the webhook. If
> no secret is configured, no `X-FS-Signature` header is sent.

Node:

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

function verify(rawBody, signatureHeader, secret) {
  if (!signatureHeader) return false;
  const expected = crypto.createHmac('sha256', secret).update(rawBody).digest('base64');
  try {
    return crypto.timingSafeEqual(Buffer.from(signatureHeader), Buffer.from(expected));
  } catch {
    return false;
  }
}

```

Python:

```python
import hmac, hashlib, base64

def verify(raw_body: bytes, signature_header: str, secret: str) -> bool:
    if not signature_header:
        return False
    expected = base64.b64encode(
        hmac.new(secret.encode(), raw_body, hashlib.sha256).digest()
    ).decode()
    return hmac.compare_digest(signature_header, expected)

```

After verifying, iterate `payload.events` and dispatch on each `event.type`.
Dedupe on `event.id` — automatic retries reuse the same id (manual retries get new
ids). FastSpring auto-retries over HTTPS until your endpoint returns HTTP `200`.

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

## Common Event Types

| Event | Triggered When |
| --- | --- |
| `order.completed` | An order is successfully completed |
| `order.failed` | An order fails |
| `order.canceled` | An order is canceled |
| `subscription.activated` | A new subscription is activated |
| `subscription.charge.completed` | A recurring subscription charge succeeds |
| `subscription.charge.failed` | A recurring subscription charge fails |
| `subscription.updated` | A subscription is updated |
| `subscription.canceled` | A subscription is canceled |
| `subscription.deactivated` | A subscription is deactivated |
| `return.created` | A return/refund is created |

> For the full event reference, see [FastSpring Webhooks](https://developer.fastspring.com/reference/webhooks-overview).

## Environment Variables

```bash
FASTSPRING_WEBHOOK_SECRET=your_hmac_sha256_secret   # From Dashboard → Developer Tools → Webhooks → Configuration

```

## Local Development

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

```

Optionally allowlist FastSpring's source IP `107.23.30.83`.

## Reference Materials

* [references/overview.md](https://github.com/hookdeck/webhook-skills/blob/main/skills/fastspring-webhooks/references/overview.md) - FastSpring webhook concepts, batched events
* [references/setup.md](https://github.com/hookdeck/webhook-skills/blob/main/skills/fastspring-webhooks/references/setup.md) - Dashboard configuration and HMAC secret
* [references/verification.md](https://github.com/hookdeck/webhook-skills/blob/main/skills/fastspring-webhooks/references/verification.md) - Signature verification details and gotchas