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Creative Workflow Helpers

CORS Header Builder & Explainer

Describe the cross-origin request your frontend makes and get the exact Access-Control-* response headers to send back — plus a plain-language explanation of what each one does. Nothing leaves your browser.

Runs in your browser v1.0.0

1. Pick a scenario

start here

Choose the situation closest to yours to load a working starting point. The headers update immediately and nothing is sent to a server.

2. Describe the request

required

Use * to allow any origin, or the exact origin (scheme + host + optional port, no path).

Comma-separated names, excluding Content-Type. Any header that is not CORS-safelisted makes the browser send a preflight.

Advanced: allowed methods, exposed headers, cache optional
Allowed methods

Sent as Access-Control-Allow-Methods in the preflight response.

Extra response headers page JavaScript may read, beyond the safelisted ones.

How long the browser may reuse the preflight result. 0 disables caching.

3. Response headers to send

Actual response


                        


                        

                            
                            
                            
                            
                        


                        

                    

                


                

                    

                        
What each header does

                    

                    

                        
    
                    
    
                
    
            
    
        
    
    
    

    
    
        
    
            
    How it works
    
        
    
        
    
            
    
                The tool models the browser's CORS rules locally. It decides whether a preflight is needed
                from the method, the Content-Type value and the request headers, then assembles
                the matching Access-Control-Allow-* headers. Requests that are not
                CORS-safelisted (methods other than GET, HEAD and POST,
                non-safelisted headers such as Authorization, or a JSON body) trigger an
                OPTIONS preflight. The state is written to the URL fragment so a setup can be
                bookmarked or shared, and no input is ever sent to a server.
            
    
        
    
    
    

    

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