What does cross-origin resource sharing (CORS) control?

Cross-origin resource sharing (CORS) is a security feature implemented by browsers that regulates how web applications interact with resources from different origins or domains. This mechanism is primarily designed to allow or deny requests for resources that come from different origins while preventing unauthorized access.

The correct response highlights that CORS enables the ability to request resources from multiple domains. When a web application attempts to fetch resources from a different domain than the one that served the original page, CORS comes into play. If the server hosting the resource supports cross-origin requests, it will send specific HTTP headers that indicate which domains are permitted to access the resource and under what conditions. This allows for more flexible interactions between web services while maintaining security by defining and enforcing rules around these cross-origin requests.

In essence, CORS is crucial for enabling safe and intended interoperability between different web services and domains, making it possible for developers to build more comprehensive web applications that can leverage resources across various origins. Understanding this is essential for effective web development and ensuring that applications function correctly while adhering to security policies.