Filestack webhook setup

Filestack Webhook Setup

Webhook Event Types

Event	When it fires
fp.upload	File successfully uploaded and stored
fp.converse	Image conversion (filepicker-converse) completed
fp.delete	File deleted
fp.overwrite	File overwritten
fp.video_converse	Video conversion completed
fp.scan	Antivirus scan completed
fp.export	File exported to cloud storage
fs.workflow	Workflow pipeline completed

Register a Webhook URL

Webhook registration is done through the Filestack Developer Portal UI — there is no public REST endpoint for creating webhooks. Walk the user through:

1. Sign in at https://dev.filestack.com/
2. Open the app whose events you want to receive
3. Navigate to Webhooks in the left nav
4. Click Add Webhook, paste the receiver URL (https://yourdomain.com/filestack-webhook)
5. Select the events to subscribe to (e.g. fp.upload, fp.video_converse)
6. Copy the generated webhook secret — it appears only once, you'll need it for signature verification (see below)

If the user asks for an API-based registration flow, explain that this isn't currently exposed publicly — they have to use the portal. (There is an internal admin endpoint but it is gated by admin auth and not customer-accessible.)

Webhook Payload Shape

{
  "id": 30813791,
  "action": "fp.upload",
  "timestamp": 1710000000,
  "text": {
    "container": "filestack-uploads",
    "url": "https://cdn.filestackcontent.com/abc123XYZ",
    "filename": "image.jpg",
    "client": "Computer",
    "key": "abc123XYZ",
    "type": "image/jpeg",
    "status": "Stored",
    "size": 102400
  }
}

Signature Verification

Filestack signs webhooks with HMAC-SHA256 using a per-webhook secret (created in the Developer Portal when configuring the webhook — this is NOT the app secret). The signature covers "{timestamp}.{body}" — the FS-Timestamp header value, a dot, and the raw request body.

Headers sent by Filestack:

• FS-Signature — HMAC-SHA256 hex digest
• FS-Timestamp — Unix timestamp (string) used in signing

Node.js

import { createHmac } from 'crypto';
import type { Request, Response } from 'express';

export function verifyFilestackSignature(req: Request): boolean {
  const signature = req.headers['fs-signature'] as string;
  const timestamp = req.headers['fs-timestamp'] as string;
  if (!signature || !timestamp) return false;

  // Filestack signs "{timestamp}.{body}" — must match exactly
  const signPayload = `${timestamp}.${req.rawBody}`;
  const expected = createHmac('sha256', process.env.FILESTACK_WEBHOOK_SECRET!)
    .update(signPayload)
    .digest('hex');
  return signature === expected;
}

export function webhookHandler(req: Request, res: Response): void {
  // CRITICAL: Return 200 BEFORE processing — prevents duplicate delivery on timeout
  if (!verifyFilestackSignature(req)) {
    res.status(401).send('Invalid signature');
    return;
  }
  res.status(200).send('ok');

  // Process asynchronously after responding
  setImmediate(() => processEvent(req.body));
}

Python (Flask)

import hmac, hashlib, os, threading
from flask import request, jsonify

def verify_signature(raw_body: bytes, timestamp: str, signature: str) -> bool:
    # Filestack signs "{timestamp}.{body}"
    sign_payload = f"{timestamp}.{raw_body.decode('latin-1')}"
    expected = hmac.new(
        os.environ['FILESTACK_WEBHOOK_SECRET'].encode('latin-1'),
        sign_payload.encode('latin-1'),
        hashlib.sha256
    ).hexdigest()
    return hmac.compare_digest(expected, signature)

@app.route('/filestack-webhook', methods=['POST'])
def webhook():
    sig = request.headers.get('FS-Signature', '')
    ts = request.headers.get('FS-Timestamp', '')
    if not verify_signature(request.get_data(), ts, sig):
        return jsonify({'error': 'invalid signature'}), 401

    # Acknowledge immediately before any slow processing
    threading.Thread(target=process_event, args=(request.json,)).start()
    return jsonify({'status': 'ok'}), 200

Go

import (
    "crypto/hmac"
    "crypto/sha256"
    "encoding/hex"
    "fmt"
)

func verifySignature(body []byte, timestamp, signature, appSecret string) bool {
    // Filestack signs "{timestamp}.{body}"
    signPayload := fmt.Sprintf("%s.%s", timestamp, string(body))
    mac := hmac.New(sha256.New, []byte(appSecret))
    mac.Write([]byte(signPayload))
    expected := hex.EncodeToString(mac.Sum(nil))
    return hmac.Equal([]byte(expected), []byte(signature))
}

Critical Patterns

Return 200 immediately, then process async. Filestack's webhook consumer has a configurable timeout (default ~30s). If your handler times out, Filestack retries — leading to duplicate processing. Always acknowledge (200/201/204) before doing any slow work.

Handlers must be idempotent. Filestack retries failed deliveries up to 5 times with backoffs [10s, 60s, 5min, 15min, 1hr] (per the production webhook consumer's RESEND_TIMEOUTS). Note: the public docs sometimes quote a different cadence (3 attempts at 5min/30min/12hr) — the production schedule is the one above. Success codes are 200, 201, 204. Use the id field from the payload as an idempotency key.

Use raw body for signature verification. JSON parsers may reformat the body, invalidating the signature. Capture the raw bytes before parsing:

// Express: use express.raw() for the webhook route
app.post('/filestack-webhook', express.raw({ type: 'application/json' }), webhookHandler);