What does CORS stand for in the context of web applications?

CORS stands for Cross-Origin Resource Sharing, which is a crucial security feature implemented by web browsers. It governs how web applications running at one origin can request resources from another origin. An origin is defined by the combination of the protocol (HTTP or HTTPS), domain, and port.

In practical terms, when a web application attempts to make a request to a different origin, the browser checks if that origin allows such requests. It does this through the use of HTTP headers. If the server at the other origin permits the request, it responds with the appropriate CORS headers, allowing the request to proceed. For example, if a JavaScript application hosted on domain A wants to access an API hosted on domain B, CORS headers must be correctly configured on the API server to allow the request from domain A.

This mechanism is essential for maintaining the security of web applications by preventing unauthorized requests and cross-site scripting attacks. Understanding CORS is vital for developers working with APIs and frontend technologies, as it directly impacts how applications communicate with each other across the web.