You Still Struggle with CORS Even After Reading Docs
4 days ago
- #web-development
- #security
- #CORS
- CORS (Cross-Origin Resource Sharing) is a security feature implemented in browsers to restrict cross-origin HTTP requests initiated from scripts.
- CORS errors are common in web development, especially when a client application tries to access resources from a different origin without proper permissions.
- Origins are defined by the combination of scheme (protocol), host, and port. Requests are considered same-origin only if all three match.
- SOP (Same-Origin Policy) is a foundational security measure that restricts how documents or scripts from one origin can interact with resources from another origin.
- CORS provides a way to relax SOP by allowing servers to specify which origins are permitted to access their resources via HTTP headers.
- There are three main CORS scenarios: Preflight Request (checks permissions before sending the main request), Simple Request (no preflight, meets specific conditions), and Credentialed Request (includes authentication).
- To resolve CORS issues, servers must include the correct 'Access-Control-Allow-Origin' header. Wildcard (*) can be used but is insecure for credentialed requests.
- Developers can bypass CORS in development using tools like Webpack Dev Server's proxy feature, but this is not a solution for production environments.
- Attempting to bypass CORS by embedding resources in tags like <img> or <script> does not allow JavaScript access to the response data.
- Understanding CORS is crucial for both frontend and backend developers to collaborate effectively in resolving related issues.