In order to prevent duplication of webhooks, we have introduced idempotent header keys for webhooks. The new X-Contentful-Idempotency-Key header is a unique SHA256 value that is assigned to individual webhooks when fired. In rare cases, webhooks can fire twice for a single action. The new key allows you to set up filtering in your infrastructure to drop a duplicative webhook if the key value matches another very recent webhook request.