CORS

Cross-Origin Resource Sharing (CORS) is a security mechanism implemented in web browsers that allows web applications running at one origin (domain, protocol, and port) to request resources from a different origin. It uses HTTP headers to enable servers to specify which origins are permitted to access their resources, preventing malicious cross-origin requests while allowing legitimate ones. CORS is essential for modern web development where APIs and services are often hosted separately from the frontend applications that consume them.

Also known as: Cross-Origin Resource Sharing, Cors, Cross Origin Resource Sharing, CORS policy, Cross-domain requests

Why learn CORS?

Developers should learn CORS when building web applications that need to make cross-origin HTTP requests, such as when a frontend app hosted on one domain needs to fetch data from an API on another domain. It is crucial for security to prevent unauthorized cross-site requests while enabling legitimate integrations, and understanding CORS helps debug common issues like preflight requests, access control headers, and browser restrictions. Use cases include single-page applications (SPAs), microservices architectures, and third-party API integrations.

Learning Resources

• docs: MDN Web Docs: CORS
• video: CORS in 100 Seconds (Fireship)
• tutorial: Enable CORS: A Guide to Cross-Origin Resource Sharing
• tutorial: CORS Tutorial on freeCodeCamp