Gift cards have largely replaced gift certificates in modern commercial use. Gift cards typically look much like credit cards and are used much like credit cards. In fact, some gift cards may actually be pre-paid credit cards. Gift cards are popular because they are convenient and can be used incrementally for multiple purchases, given suitable funds. They are difficult to forge and in some circumstances can be replaced if lost. Most gift cards have various contractual restrictions including, commonly, being non-transferable and expiring after a certain period of time.