Why does Next.js open the page as a file?

Question

Node.js

Fetch API cannot load file:///C:/ ..... /.next/server/static/development/pages/index.js. URL scheme must be "http" or "https" for CORS request.
This is what the browser console says when I try to make a request to the graphql api server. I don't understand why Next.js opens the page as a local file, because it should open it through localhost:3000/....
Has anyone faced such a task?