## TL;DR

Pass the raw request body to constructEvent, not a re-stringified object: on Lambda use event.body as received (the raw string), since any JSON.stringify round-trip changes the bytes and breaks the signature.

## Steps

1. On AWS Lambda (via API Gateway), stripe.webhooks.constructEvent failed with No signatures found matching the expected signature for payload. API Gateway hands the Lambda a parsed JSON object as the body, and JSON.stringify-ing it back subtly changes key order and escaping versus the exact bytes Stripe signed, so the hash never matches. A second common trap in the same thread: using the wrong secret, e.g. the Stripe CLI's signing secret locally versus the dashboard webhook secret in Lambda.

2. Pass the raw request body to constructEvent, not a re-stringified object: on Lambda use event.body as received (the raw string), since any JSON.stringify round-trip changes the bytes and breaks the signature. Also verify you are using the webhook signing secret (whsec_..., from Dashboard > Developers > Webhooks > Reveal), not your API secret (sk_...) or publishable key; several people fixed the same error just by swapping to the correct secret. Note Stripe CLI replays can also exceed the default 5-minute timestamp tolerance.

## When to use

You are seeing this: On AWS Lambda (via API Gateway), stripe.webhooks.constructEvent failed with No signatures found matching the expected signature for payload. Use this skill when you run into "Stripe webhook signature mismatch on AWS Lambda: use raw event.body and the whsec_ secret".

## When not to use

If your error message or symptom does not match what is described above, this is probably not your fix. Search for your exact error text instead of forcing this one to fit.

## Versions

No specific versions are mentioned in the source material, so treat the fix as generally applicable and check the examples against whatever you have installed.

## Why this happens

The original report does not dig into a root cause. It documents the symptom and the fix that resolved it.

## Edge cases

- Also verify you are using the webhook signing secret (whsec_..., from Dashboard > Developers > Webhooks > Reveal), not your API secret (sk_...) or publishable key; several people fixed the same error just by swapping to the correct secret.

- Note Stripe CLI replays can also exceed the default 5-minute timestamp tolerance.