It's dead simple to use: send a request to `https://httpthing.com/{endpoint}` and the request will be logged for you to inspect. A unique URL will be returned so you can easily see the request details in a browser.
If you want to see all requests sent to `{endpoint}`, just go to `https://httpthing.com/_/{endpoint}`. Requests are public, so it's best to use a randomly generated `{endpoint}`.
Simple, I know, but I've started using it for all of my webhook testing. Let me know if you find it simple and useful as well.