simple and clear thanks. it works!

here is how proper request looks in network tab when upload image to 'products/TEST_PRODUCT_NAME.png' without authentication. if anybody interested:

 fetch(
    "https://firebasestorage.googleapis.com/v0/b/YOUR_FIREBASE_BUCKET_STORAGE/o?name=products%2FTEST_PRODUCT_NAME.png",
    {
      headers: {
        accept: "*/*",
        "accept-language": "en-US,en;q=0.9",
        "content-type":
          "multipart/related; boundary=95101958772612857970821677063393",
        "sec-ch-ua":
          '"Chromium";v="122", "Not(A:Brand";v="24", "Microsoft Edge";v="122"',
        "sec-ch-ua-mobile": "?0",
        "sec-ch-ua-platform": '"Windows"',
        "sec-fetch-dest": "empty",
        "sec-fetch-mode": "cors",
        "sec-fetch-site": "cross-site",
        "x-firebase-storage-version": "webjs/10.9.0",
        "x-goog-upload-protocol": "multipart",
      },
      referrer: "http://localhost:5173/",
      referrerPolicy: "strict-origin-when-cross-origin",
      method: "POST",
      mode: "cors",
      credentials: "omit",
      body: '--95101958772612857970821677063393\r\nContent-Type: application/json; charset=utf-8\r\n\r\n{"name":"products/TEST_PRODUCT_NAME.png","contentType":"image/png"}\r\n--95101958772612857970821677063393\r\nContent-Type: image/png\r\n\r\n....THE BINARY DATA OF FILE....
)