Stop the CORS Hate!

Cross-Origin Resource Sharing

CORS is key to web data sharing, but managing policies across domains is tricky. Developers struggle with errors and restrictions. We simplify CORS concepts, errors, and fixes with clear strategies.

CORS Documentation CORS Tester

CORS Errors

CORS Policy Blocks Redirects

When a browser makes a cross-origin request to a URL that responds with a redirect (3xx status)...

Credentials Requests Not Allowed

This error occurs when a frontend request includes credentials (such as cookies or authentication headers), but the...

Invalid Access-Control-Allow-Origin Value

The Invalid Access-Control-Allow-Origin Value error occurs when the server responds with an incorrect or malformed...

Method Not Allowed by CORS

The "Method Not Allowed by CORS" error occurs when a client (browser or API consumer) sends an HTTP request...

Misconfigured Access-Control-Allow-Credentials

The "Access-Control-Allow-Credentials" header is used in Cross-Origin Resource Sharing (CORS) to allow the...

Missing Access-Control-Allow-Headers

The `Access-Control-Allow-Headers` header is used in CORS (Cross-Origin Resource Sharing) to specify which...

No Access-Control-Allow-Origin Header

No Access-Control-Allow-Origin Header error occurs when a web application running in a browser tries to make a request...

Origin Mismatch

An Origin Mismatch error in CORS happens when the browser detects that the request's `Origin` header...

Preflight Request Failed

The error CORS preflight request failed occurs when the browser sends a preflight request (an OPTIONS request) to the...

Response Type Not Allowed

The "Response Type Not Allowed" error in CORS usually occurs when the server does not properly set the...

Wildcard Not Allowed for Access-Control-Allow-Headers

The `Access-Control-Allow-Headers` response header in CORS (Cross-Origin Resource Sharing) specifies...