CORS Error Reference
1 model · 5 error codes
Browse CORS error code collections, meanings, and related context across the current corpus.
About CORS Error Reference
Cross-Origin Resource Sharing (CORS) is a security mechanism enforced by modern web browsers that restricts how a web page can request resources from a different domain. When a request violates the CORS policy—due to missing headers, invalid origins, or preflight failures—the browser blocks the response and logs a CORS error in the developer console.
CORS errors are strictly a client-side enforcement mechanism. The server may have successfully processed the request and sent a response, but the browser refuses to hand that response to the calling JavaScript code if the appropriate Access-Control- headers are missing or mismatched.
FixerCode documents 5 specific CORS error conditions across 1 model. Each entry decodes the exact browser console message, explains which CORS header was missing or invalid, and provides the necessary server or proxy configuration to resolve the cross-origin policy block.
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Frequently Asked Questions
CORS errors are caused by a web application attempting to make an AJAX/fetch request to a different domain, subdomain, or port without the destination server explicitly permitting it via Access-Control- HTTP headers.
In development, you can use a local proxy (like Webpack Dev Server proxy or Next.js rewrites) to make requests appear as same-origin. Alternatively, you can configure your local API server to return Access-Control-Allow-Origin: * for development environments.
Postman, curl, and backend servers are not web browsers; they do not enforce the Same-Origin Policy or require CORS headers. CORS is strictly a browser security feature designed to prevent malicious websites from making unauthorized requests on behalf of the user.