After integrating Stripe into multiple projects, here are the
errors I see (and make) every time:
**1. Parsing the body before Stripe reads it**
If you use `await req.json()` in your webhook route instead of
`await req.text()`, signature verification always fails.
Took me an embarrassing amount of time to figure this out.
**2. Missing userId in metadata**
When creating a Checkout Session, if you don't pass
`metadata: { userId: user.id }`, your webhook handler
has no way to know which user just paid.
**3. Not handling idempotency**
Stripe retries webhooks on non-200 responses. If your handler
crashes halfway, it fires again — and you update the DB twice.
Always check if the event was already processed.
**4. cancel_immediately instead of cancel_at_period_end**
Users hate losing access they already paid for.
Always default to cancel_at_period_end.
I wrote a full guide on this if anyone wants the complete setup.
DM me and I'll send it.
Happy to answer questions in the comments.