I've faced with issue while proxy http request with multipart form data by NextJS. I have to send file from a client fide to next js, after that - to FastApi service.
The problem was:
fetch("https://127.0.0.1:3000/api/newfile", {
method: "POST",
headers: { "Content-Type": "multipart/form-data" },
body: new FormData(form)
});