A tape viewer was a device that allowed one to watch the information recorded on verism tapes. The Sarpeidon library used tape viewers in order to allow users to decide which era of the planet's history they wished to enter to escape from the effects of the Beta Niobe supernova.

In 2269, James T. Kirk, Leonard McCoy and Spock used these viewers at Mr. Atoz's suggestion. Later, Kirk reasoned (correctly) that the device was tied into the atavachron. (TOS: "All Our Yesterdays")