This guide covers everything you need to test Square webhooks — how to inspect the raw payload, verify the signature, forward events to localhost, and reproduce any delivery in your local development environment without needing a real Square event.
How to Test Square Webhooks with WebhookWhisper
- Create a free endpoint — click Create Live Endpoint above to get a permanent public HTTPS URL (no account required to try)
- Register the URL in Square — paste the WebhookWhisper URL into Square's webhook settings
- Trigger a test event — use the one-click test payload sender or trigger a real event in Square
- Inspect the request — see the full headers, raw body, and Square signature header in real time
- Forward to localhost — add a forwarding rule to relay the event to your local handler (e.g.
http://localhost:3000/webhooks/square)
Square Webhook Signature Verification
Square signs webhook deliveries using HMAC-SHA256. The signature is sent in the x-square-hmacsha256-signature header. Always verify this signature before processing the payload to ensure the request came from Square and was not tampered with in transit.
Node.js Verification
const crypto = require('crypto')
const express = require('express')
const app = express()
app.post('/webhooks/square',
express.raw({ type: 'application/json' }),
(req, res) => {
const secret = process.env.SQUARE_WEBHOOK_SECRET
const signature = req.headers['x-square-hmacsha256-signature']
// Compute expected HMAC — always use raw body, never parsed JSON
const expected = crypto
.createHmac('sha256', secret)
.update(req.body)
.digest('hex')
if (!crypto.timingSafeEqual(Buffer.from(signature || ''), Buffer.from(expected))) {
return res.status(401).json({ error: 'Invalid signature' })
}
const event = JSON.parse(req.body)
// Process event here — respond first, process async for slow operations
res.json({ received: true })
}
)Python (FastAPI) Verification
import hashlib, hmac, os
from fastapi import FastAPI, Request, HTTPException
app = FastAPI()
@app.post('/webhooks/square')
async def webhook(request: Request):
secret = os.environ['SQUARE_WEBHOOK_SECRET'].encode()
raw_body = await request.body()
signature = request.headers.get('x-square-hmacsha256-signature', '')
expected = hmac.new(secret, raw_body, hashlib.sha256).hexdigest()
if not hmac.compare_digest(signature, expected):
raise HTTPException(status_code=401, detail='Invalid signature')
payload = await request.json()
return {'received': True}Common Square Webhook Errors
| Error | Cause | Fix |
|---|---|---|
| 401 Unauthorized | Signature mismatch — body parsed before verification | Use raw body bytes for HMAC, never parsed JSON |
| Timeout | Handler takes longer than Square's timeout window | Respond with 200 immediately, process async in background |
| Duplicate events | Your handler returned non-2xx, causing retries | Deduplicate using the event ID field |
| Missing events | Wrong URL registered or endpoint returning errors | Use WebhookWhisper to confirm the exact delivery URL and response |
Forward Square Webhooks to Localhost
Use WebhookWhisper to receive Square webhook events at a public HTTPS URL and relay them to your local development server — no tunnel, no CLI install, no public server required.
- Create a WebhookWhisper endpoint and paste it into Square's webhook settings
- In the Forwarding tab, set target URL to
http://localhost:3000/webhooks/square - Every Square event appears in the inspector and hits your local handler simultaneously
- Use event replay (Pro) to re-send any captured event without triggering a new action in Square
FAQ
Do I need a Square account to test webhooks?
No. WebhookWhisper includes a one-click Square sample payload so you can fire a realistic test event and verify your handler without a Square account or triggering a real Square action.
How do I find my Square webhook secret?
The webhook signing secret is shown in Square's developer settings or webhook configuration page. Each webhook endpoint gets its own secret — do not share secrets between endpoints.
What is the Square webhook timeout?
Most providers timeout after 5–30 seconds. If your handler does slow operations (database writes, external API calls), respond with HTTP 200 immediately and process the event in a background job to avoid triggering Square's retry logic.