Problem with the Orchestator API (preflight request/cors)

Me and my team are developing a web app that allow us to call the Ochestator. The purpose of the app is to provide our employees a web form from where transactions can be added, so it will need to call the orchestator api. These calls work properly when executed on Postman/curl, etc… But when they are made using the web app(Firefox, Chrome) it throws a CORS Policy error.

We have searched in this forum, and many people seems to have this same exact error. It seems that the header Access-Control-Allow-Origin is not sent back from the server, so the browser blocks the call.

When we generate the OAuth token from it works fine, but when we make another call, like for example retrieving folder info (or any orchestator api endpoint), the error occurs. This an example of the code that performs this action:

async function getIdCarpeta(token, carpetaOrchestrator){
    var requestOptions = {
        method: 'GET',
        mode: "cors",
        headers: {
            "Content-type": "application/json",
            Authorization: `Bearer ${token}`
        redirect: 'follow'

    let resp = await fetch(`****/pr****/orchestrator_/odata/folders?$filter=DisplayName eq 'folder name'`, requestOptions);
    let jsonResp = await resp.json();
    return jsonResp.value[0].Id;

We know that we can use a chrome extension or a proxy to avoid CORS, but this is no the solution we need. Besides, we use the UiPath Cloud, so we can’t edit any file. Is there any way to perform api calls from a web navigator?

Thank you.

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What happens if you remove from your code the mode: "cors" and redirect: 'follow'?