There are few places in the world where you can buy things with digital currencies like Bitcoin. But why would you want to? Since the first of the year, Bitcoin and other so-called cryptocurrencies have exploded in value, making them one of the hottest investments on the planet, and far too valuable to spend.

While the Standard & Poors index of 500 stocks has risen by about 7 percent since January, a unit of Bitcoin has gained 130 percent, climbing from $961 to Friday’s price of about $2,225. The second-most-popular cryptocurrency, Ether, did even better, soaring nearly 1,900 percent in the same period, from about $8 to about $164. Other digital money types, with names like Ripple and Litecoin, are also on the rise.

Cryptocurrencies are a form of money created by computer networks instead of by government-sponsored banks. They enable people to make fast, anonymous transactions at virtually no cost while using digital encryption to create an indelible record of every transaction. Cryptocurrencies eliminate the need for banks to act as middlemen, making transactions almost as fast and cheap as sending an e-mail.