Problema CORS con XMLHttpRequest

[techno]

Ciao a tutti, ho quest script:

function _(el) {
     return document.querySelector("#" + el);
}

function uploadFile(){
      var file = _("fileUpload").files[0];


       let formdata = new FormData();
       formdata.append("file_upload", file);

       const ajax = new XMLHttpRequest();
       ajax.upload.addEventListener("progress", progressHandler, false);
       ajax.upload.addEventListener("complete", completeHandler, false);
       ajax.upload.addEventListener("error", errorHandler, false);
       ajax.upload.addEventListener("abort", abortHandler, false);

       ajax.open("POST", "upload_file.php");
       ajax.send(formdata);
}

Mi da questo errore:

from origin 'null' has been blocked by CORS policy: Cross origin requests are only supported for protocol schemes: chrome, chrome-extension, chrome-untrusted, data, http, https, isolated-app.