What is cross-domain-cookies?

This repository is a hands-on demonstration of how web browsers handle cookies when a website on one domain tries to talk to a service on a completely different domain. It is not a tool or application you would deploy, but rather a teaching example showing why cross-origin cookie sharing is tricky and often fails in practice. To use it, you run two small local servers that pretend to be different websites. You visit the first server in your browser to generate a cookie, which is a small piece of data used to remember who you are. Then, you visit the second server. The project shows that while you can sometimes configure the servers to pass that cookie between them, the second website cannot actually read the data inside it due to built-in browser security rules. The audience for this is developers or students learning about web security, particularly the concepts of "cross-origin resource sharing" (CORS) and cookie policies. Someone might use this if they are building a project where their front-end application and back-end database live on different web addresses, and they are trying to figure out why their users keep getting logged out or why their requests are being blocked. What makes this project notable is that it deliberately shows you a scenario that works, and then walks you through changing a single setting to make it fail. By doing this, it illustrates that sending cookies across different domains requires strict, exact configuration that is hard to achieve in the real world. It serves as a practical warning about the limitations of cross-domain authentication.