How Do I Set Access-Control-Allow-Headers in Strapi v4?

To set the Access-Control-Allow-Headers response header in Strapi v4, you will need to use a custom middleware. Middleware in Strapi are functions that are executed before or after the request reaches the route handler.

Here is an example of how you can create a custom middleware that sets the Access-Control-Allow-Headers response header:

// In your Strapi project, create a new file at:
// /extensions/cors/config/middleware.json

module.exports = { 
   settings: { // Set the allowed headers for CORS    
       allowedHeaders: ['Content-Type'] 
   }
} 

// In your Strapi project, create a new file at:
// /extensions/cors/config/policies/cors.js

module.exports = (ctx, next) => { 
    // Set the allowed headers on the response object      
    ctx.response.set('Access-Control-Allow-Headers', 
    strapi.config.middleware.settings.allowedHeaders.join(',')); 
    // Call the next middleware  
    return next(); 
 }

After you have created these files, you will need to enable the custom middleware in your Strapi project. To do this, open the /config/middleware.json file in your Strapi project and add the following entry to the policies array:

// /config/middleware.json 
{  
    "policies": [    // Add the cors middleware to the policies array           "cors"  
    ]
}

This will enable the custom CORS middleware in your Strapi project, and it will set the Access-Control-Allow-Headers response header to include the Content-Type header.

I hope this helps! Let me know if you have any other questions.