Charles vs Motty: What are the differences?

Charles: HTTP proxy / HTTP monitor / Reverse Proxy. Charles is a web proxy (HTTP Proxy / HTTP Monitor) that runs on your own computer. Your web browser (or any other Internet application) is then configured to access the Internet through Charles, and Charles is then able to record and display for you all of the data that is sent and received; Motty: Modern and simple way to test client services. Motty provides the simpler way to test your client services. It is a web application that gives you ability to create your own custom responses, so you can intuitively and easily mock http responses.

Charles and Motty can be categorized as "API" tools.

Motty is an open source tool with 62 GitHub stars and 4 GitHub forks. Here's a link to Motty's open source repository on GitHub.