We're making a project with both frontend and backend, there is auth form, which should make POST request to backend, giving JSON object with email and password of user. If I specify 'Content-Type': 'application/json', then we see 2 requests instead of one: options (first) and post (second) requests, that results an error even with running backend (screenshot provides errors without running backend, only frontend) 
const response = await fetch(url, {
method: 'POST',
headers: {
'Content-Type': 'application/json'
},
body: dataArr
});
But when I specify 'Content-Type': 'application/x-www-form-urlencoded' and body: JSON.stringify(data), then there is no options request, only post one, but the data is then passed not as json object, so backend can't resolve the request properly. It awaits for json object
const response = await fetch(url, {
method: 'POST',
headers: {
'Content-Type': 'application/x-www-form-urlencoded'
},
body: JSON.stringify(data)
});
Is there any way to pass data as JSON object via POST properly without OPTIONS requests? backend uses python FastAPI
OPTIONSrequest), and aPOSTrequest can only be simple if it has aContent-Typeofapplication/x-www-form-urlencoded,multipart/form-data, ortext/plain. So there is no way to do this in a browser.OPTIONSrequest, what problem are you actually trying to solve? Most likely, this is a CORS issue, where the solution is to learn how to set up CORS properly in FastAPI.