Seems like a simple issue but everywhere else suggested adding "application/json" in 'headers' which I have tried.

'Accept'and 'Content-Type' are both "application/json". Also tried both json and stringfy 'Body' but keep getting 415 on Chrome extension JavaScript.

textArraySample = ["sample","sample2"];
var serverUrl = "https://webappcontentnotification.azurewebsites.net/api/ContentUpload";
const body={
    "textbatch":textArraySample,
    "userId": userId,
    "url": window.location.href
}
let result = 
fetch(serverUrl, {
    method: 'POST',
    mode: "no-cors",
    headers: {
        'Accept': "application/json",
        'Content-Type': "application/json"
    },
    body: JSON.stringify(body)
    })
.then(response => {
    console.log('response:', response);
})
.catch((error) => {
    console.log('Error:', error);
});

Update: seems like "Content-Type" is not correctly set