Rails CORS Guide: What It Is and How to Enable It

Cross-origin resource sharing (CORS) is an HTTP-header based security mechanism crucial for web application developers, especially when exposing APIs to the internet. CORS restricts interactions to the same origin, defined by protocol, domain, and port, thus blocking requests from different origins, even if the front-end and back-end are on the same server. Developers can identify CORS-related issues through error messages in the browser console and resolve them by configuring CORS in applications like Rails using the rack-cors gem. Proper configuration involves specifying allowed origins and HTTP methods to ensure security while avoiding misconfigurations like using wildcard origins, which can expose APIs to anyone on the internet. Additional considerations include middleware positioning and handling static files, as well as the importance of further security measures like SQL injection protection. The article, written by Dawid Ziolkowski, emphasizes that understanding and correctly implementing CORS is straightforward yet essential for securing web applications.