We can't easily change the browser Accept headers (actually you can by delving into the config but it's a bit of a hassle), so can we change the behavior on the server? When working on AJAX applications I tend to not be interested in XML results and I always want to see JSON results at least during development. Which for once actually seems more sensible. Interestingly enough Internet Explorer 9 also displays JSON because it doesn't include an application/xml Accept header:Īccept: text/html, application/xhtml+xml, */* Or leaving the Accept header out altogether should give you a JSON response. To verify that Web API indeed defaults to JSON output by default you can open the request in Fiddler and pop it into the Request Composer, remove the application/xml header and see that the output returned comes back in JSON instead.Īccept: text/html,application/xhtml+xml,*/* q=0.9 In this case it matches application/xml to the Xml formatter and so that's what gets returned and displayed. Web API inspects the entire list of headers from left to right (plus the quality/priority flag q=) and tries to find a media type that matches its list of supported media types in the list of formatters registered. In the case of browsers it turns out that most send Accept headers that look like this (Chrome in this case):Īccept: text/html,application/xhtml+xml, application/xml q=0.9,*/* q=0.8 This automatic negotiation is one of the great features of Web API because it makes it easy and transparent to request different kinds of output from the server. Web API checks the HTTP Accept headers of a request to determine what type of output it should return by looking for content typed that it has formatters registered for.

If I preview a Web API request in most browsers I get an XML response like this: While I can't debug all requests this way, GET requests are easy to test in the browser especially if you have JSON viewing options set up in your various browsers. When working on AJAX application I like to test many of my AJAX APIs with the browser while working on them. ASP.NET Web API's default output format is supposed to be JSON, but when I access my Web APIs using the browser address bar I'm always seeing an XML result instead.

Xml formatter online