Understanding CORS

We might have already encountered the term CORS several times when creating our applications as developers. Still, we may ask questions such as what does CORS do? Or what is the advantage of implementing CORS in our application? With these questions in mind, we will dive deeply, in this section, into the concepts and features of CORS and understand how it is used to secure our applications.

CORS is a header-based mechanism that allows a server to define a set of domains, schemes, or ports permitted to access the application’s resources. CORS is commonly used in REST APIs. Different frontend applications can access the APIs under our backend applications, especially in complex architectures. We don’t want our APIs to be accessed by unknown applications, and CORS is responsible for securing this part.

Let’s see a simple example of a cross-origin request. Say we have a frontend application with a domain of https://domain-one.com and a backend...