Request.redirect could be "follow", "error" or "manual". If it is "follow", fetch() API follows the redirect response (HTTP status code = 301,302,303,307,308). If it is "error", fetch() API treats the redirect response as an error. If it is "manual", fetch() API doesn't follow the redirect and returns an opaque-redirect filtered response which wraps the redirect response.
Docs: https://developer.mozilla.org/en-US/docs/Web/API/Request