Even though Tumblr only makes group chat messages available to the public (i.e., the other chat participants) for a short amount of time before their expiration and deletion from public view, group chat messages and related information (e.g., list of chat participants) will be retained by Tumblr for internal purpose (e.g., security audits), and/or as required by law (e.g., pursuant to a litigation hold notice) after they have disappeared from public view.