Delivery

Content type

Fractal ID uses application/json content type to deliver the JSON payload directly as the body of the POST request.

Expected response

Fractal ID expects your server to reply with response code 2xx to identify successful delivery. All response codes outside this range, including 3xx codes, will indicate to Fractal ID that you did not receive the webhook.

Fractal ID will make sure to send notification successfully at least once to the client. There is a possibility of receiving the same successful webhook notification multiple times, but in very rare cases. This means you should likely want to ensure your endpoint is idempotent.

Retrying sending notifications

Fractal ID will retry to send webhooks notification if:

• Client server failed to respond in 10 seconds.

• Client server is unavailable (network errors).

• Client server returns other response code than 2xx.

Fractal ID uses exponential backoff to retry events.

Example retry times table

Retries	Next retry in seconds
1	20
2	40
3	80
5	320
10	10240
15	86400
20	86400

Order of delivery

The order of callbacks to webhook endpoints is not guaranteed.

For, e.g., two subsequent status changes, if initial attempt to deliver first notification fails it's being scheduled for retry. Second notification may arrive earlier than the retry on the first notification happens.

To mitigate the risk of setting incorrect user status based on received webhook callbacks we encourage you to keep track of the timestamp fields of the status change notifications and compare them internally, or retrieve user information upon getting a webhook callback.

Example delivery

Suppose for the given example the secret token is 9d7e80c0f169ab94d34392d64617b7517fb07c40.

POST /callback HTTP/1.1
Host: localhost:3001
X-Fractal-Signature: sha1=9e581dd775e5ba87e9839b595d6eb0d784ecfdb6
Content-Type: application/json
{"type":"verification_approved","data":{"level":"basic","user_id":"b5c5a2cd-643e-444b-9591-e7b25fec997d","timestamp":"2020-10-09T10:50:32Z"}}