Hello, I followed the Kotlin full-stack web app tutorial to make my web app, and I am now working on deploying it to Heroku. I used MongoDB Atlas to connect Heroku and my database, and the code used is very much the same in the tutorial itself. I encountered a problem where when I POST through the frontend, I receive a 403 error. The strange thing is, GET and DELETE requests work just fine, and even when I POST with something like curl, it works perfectly! The only problem is that POST doesn't work from the frontend. When this function is called from the frontend:

suspend fun addShoppingListItem(shoppingListItem: ShoppingListItem) {

    <http://jsonClient.post|jsonClient.post><Unit>(endpoint + ShoppingListItem.path) {


        contentType(ContentType.Application.Json)
        body = shoppingListItem

    }

}

This is what the server does when it receives a POST request:

post {

    collection.insertOne(call.receive<ShoppingListItem>())
    call.respond(HttpStatusCode.OK)

}

but this is what I get every time I perform a POST request through my browser. Are there any help or docs I might be able to benefit from?

seems related https://youtrack.jetbrains.com/issue/KTOR-3979

It was related! As soon as I added

header(HttpHeaders.ContentType)

everything now works!