Mastering CORS: 10 Crucial Tips for Effective Implementation

Cross-Origin Resource Sharing (CORS) enables controlled API access across different domains. To implement CORS in .NET, configure it in Startup.cs using CORS middleware. Specify allowed origins using WithOrigins, restricting access to specific domains. Control allowed HTTP methods using WithMethods to filter API methods. Limit allowed headers using WithHeaders to prevent unauthorized header usage. Enable credentials with AllowCredentials() if necessary. Apply CORS policies globally or at the controller/action level. Handle preflight requests by allowing OPTIONS requests if CORS is configured correctly. Configure environment-specific CORS policies for different environments. Regularly review and update CORS policies to adapt to changing requirements. Monitoring request patterns helps ensure security and functionality.