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The web has evolved from a collection of static documents to dynamic applications rivaling native apps in their capabilities. This shift is powered by the ability of websites to effortlessly communicate with servers and APIs across the internet.
However, browsers restrict cross-origin HTTP requests by default as a security measure. This is where Cross-Origin Resource Sharing (CORS) comes in — it allows servers to specify what kinds of cross-origin access are permitted to their resources.
Mastering CORS is essential for building complex single-page apps and enabling seamless client-server interactions.
What is the Same-Origin Policy?
The same-origin policy is a core web security concept that restricts how scripts on one origin can interact with resources from another. An origin consists of a URL’s protocol, host and port. So https://example.com/page.html is an origin, and any resources on this domain, port and protocol share the same origin.
The policy blocks reading the properties of documents/windows from other origins. It also prevents the sending of cookies and AJAX requests to origins differing from the…
