Best practice to convert Dropbox shared URL to direct download link in code?

I have refer the doc, but in my case i want to extract the Content-type of a image from a link and i have tried in postman whenever i am changing hostname it is giving me that content-type properly, but keeping the hostname same and changing the query parameter to dl=1 it is giving application/binary
So what to do for getting correct content-type

const getMedia = (options) =>
  new Promise((resolve, reject) => {
    request.get(options, (err, response) => {
      if (err) {
        reject(err)
      }
      resolve(response)
    })
  })

I am doing this to get the Media and then extracting its mime type, sometimes its working and sometimes not, but by changing hostname its working fine, so i want the concrete reason or a any other solution which will be feasible for future also