Web API is used to create Services, usually web API returns XML formatted data in default in browsers. But there is option to change the output format from web API. Here is the example to change the formatting and headers of the REST format and REST response headers.

Example:

Go to WebApiConfig file and place the additional code shown below. Add the additional namespace too.

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web.Http;
using System.Net.Http.Formatting;
using Newtonsoft.Json.Serialization;
using System.Net.Http.Headers;

namespace WebApiDemo
{
    public static class WebApiConfig
    {
        public class CustomJsonFormatter : JsonMediaTypeFormatter
        {
            public CustomJsonFormatter()
            {
                this.SupportedMediaTypes.Add(new MediaTypeHeaderValue("text/html"));
            }

            public override void SetDefaultContentHeaders(Type type, HttpContentHeaders headers, MediaTypeHeaderValue mediaType)
            {
                base.SetDefaultContentHeaders(type, headers, mediaType);
                headers.ContentType = new MediaTypeHeaderValue("application/json");
            }
        }


        public static void Register(HttpConfiguration config)
        {
            config.MapHttpAttributeRoutes();
            config.Routes.MapHttpRoute(
                name: "DefaultApi",
                routeTemplate: "api/{controller}/{id}",
                defaults: new { id = RouteParameter.Optional }
            );
            config.Formatters.Add(new CustomJsonFormatter());
        }
    }
}


 Above code will support to show response in JSON format while request comes from browser.