What information can be stored on a magnetic stripe card?

The magnetic stripe card standard for financial cards (ie credit and debit cards) allow for three tracks, called, not surprisingly, tracks one, two and three.

Track one can contain up to 79 alpha numeric characters, while tracks two and three can contain up to 40 and 107 numeric characters respectively.

Note that track one is the only track in the financial card standard that can contain letters – the other tracks can contain numbers only.