Hello,
I want to propose this modification that solve a download problem in my usage in mode HTTP in non secure context.
By default, the following code works if hostname matches http://localhost:3000/ or https://mydomain.com:3000, but not if using http://mydomain.com:3000 or http://192.168.1.1:3000.
I'm using streamSaver with react and npm version 2.0.6
export function fetchFile(url, opts, filename) {
 // Use https://developer.mozilla.org/en-US/docs/Web/API/FileSystemWritableFileStream in the future
 if(opts.streamSaverPath){
 streamSaver.mitm = opts.streamSaverPath + '/mitm.html';
 console.log("Using mitm: " + streamSaver.mitm);
 }
 return fetch(url, opts).then(response => {
 const totalSize = response.headers.get('Content-Length');
 console.log("File size is: " + totalSize);
 // If the WritableStream is not available (Firefox, Safari), take it from the ponyfill
 if (!window.WritableStream) {
 console.log("Using ponyfill WritableStream");
 streamSaver.WritableStream = WritableStream;
 window.WritableStream = WritableStream;
 }
 const fileStream = streamSaver.createWriteStream(filename, {size: totalSize});
 const readableStream = response.body;
 // More optimized (mainly available in Safari)
 if (readableStream.pipeTo) {
 console.log("Using pipeTo method");
 return readableStream.pipeTo(fileStream);
 }
 console.log("Using pump method");
 // Else we create manually the pipe
 const writer = fileStream.getWriter();
 const reader = readableStream.getReader();
 const pump = () => reader.read()
 .then(res =>
 res.done ? writer.close() : writer.write(res.value).then(pump)
 );
 return pump();
 });
}