python 42 lines · 7 steps

Handling Stripe webhooks in FastAPI

A FastAPI endpoint that verifies Stripe's signature, then routes each event type to the right billing action.

Explained by highlit
FastAPI Intermediate webhooks signature-verification event-routing async payments
1import stripe
2from fastapi import APIRouter, Request, Header, HTTPException
3 
4from app.config import settings
5from app.services.billing import (
6 activate_subscription,
7 mark_payment_failed,
8 cancel_subscription,
9)
10 
11router = APIRouter(prefix="/webhooks", tags=["webhooks"])
12 
13 
14@router.post("/stripe", status_code=200)
15async def handle_stripe_webhook(
16 request: Request,
17 stripe_signature: str = Header(..., alias="Stripe-Signature"),
18):
19 payload = await request.body()
20 
21 try:
22 event = stripe.Webhook.construct_event(
23 payload=payload,
24 sig_header=stripe_signature,
25 secret=settings.STRIPE_WEBHOOK_SECRET,
26 )
27 except ValueError:
28 raise HTTPException(status_code=400, detail="Invalid payload")
29 except stripe.error.SignatureVerificationError:
30 raise HTTPException(status_code=400, detail="Invalid signature")
31 
32 obj = event["data"]["object"]
33 
34 match event["type"]:
35 case "checkout.session.completed":
36 await activate_subscription(obj["customer"], obj["subscription"])
37 case "invoice.payment_failed":
38 await mark_payment_failed(obj["customer"], obj["id"])
39 case "customer.subscription.deleted":
40 await cancel_subscription(obj["customer"])
41 
42 return {"received": True}
01 / 01
STEP 01

Walkthrough

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Three takeaways
  1. 1Always verify a webhook's signature against a shared secret before trusting its contents.
  2. 2Read the raw request body for signature checks — parsed JSON won't match the signed bytes.
  3. 3Return 200 quickly and delegate the actual work so the provider considers the event delivered.

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