The format parameter

The format query parameter specifies the output format of the response. Available formats are JSON, JSONP, API, TXT and XML. JSON and JSONP will output their respective formats. The value jsonp can be accompanied by a callback query parameter that holds as value the JavaScript function to be called as callback. The value txt is used for list responses. It is mostly useful for very large responses, as it returns the objects line by line, so the client program can use a partial response directly. The value api forces the response to be a complete HTML page with browsable links. This is also the default format if you type in a URL in a browser. The default for a request coming from any other client is json.