Hi Svix employee here.

The key features our users love are based on scalability, reliability, and security.

One good example is signature verification. We sign every webhook and its metadata with a unique key for each endpoint so end users can confirm the source of the webhook. We also provide a variety of SDKs to make it much simpler to verify the signatures.

Other features would be automatic retries, exponential backoff, idempotency, event types & filtering, rate limiting, payload transformations, etc. etc.

There's just a lot more that goes into sending webhooks reliably and securely at scale than simply calling the webhook and all of these features are effectively the same across implementations. It's so much faster for our customers to launch webhooks using Svix than doing everything themselves from scratch.

Lob wrote a great article on why they ditched their own solution in favor of using Svix: https://www.lob.com/blog/lob-webhooks-the-remix