Greasy Fork

I checked how the popular Chrome extension does this. they do a request to the youtube API, in case someone want to improve on it:

function getRemoteUploadDate(e, t) {
  fetch("https://www.youtube.com/youtubei/v1/player?prettyPrint=false", {
    method: "POST",
    headers: { "Content-Type": "application/json" },
    body: JSON.stringify({
      context: {
        client: { clientName: "WEB", clientVersion: "2.20240416.01.00" },
      },
      videoId: e,
    }),
  })
    .then((e) => {
      if (e.ok) return e.json();
      throw new Error("Network response was not ok");
    })
    .then((e) => {
      e = e.microformat.playerMicroformatRenderer;
      e.liveBroadcastDetails?.startTimestamp
        ? t(e.liveBroadcastDetails.startTimestamp)
        : e.publishDate
        ? t(e.publishDate)
        : t(e.uploadDate);
    })
    .catch((e) => {
      console.error(
        "[SYVUD]",
        "There was a problem with the fetch operation:",
        e
      );
    });
}

how to test it:

getRemoteUploadDate("video id", console.log)