Videos are available to download and watch offline as long as they are available on HISTORY Vault. Before a video is no longer available to stream or watch offline, you will see an expiration date warning you when it will go away. Once that date has passed, you will no longer see the video in your list. Additionally, if you have recently signed out of HISTORY Vault, your downloads will be reset and you will need to re-download any videos you want to be able to watch offline.
Video downloading is currently only available on iOS devices.