But every so often, some developers or an entrepreneur or a company will decide we need something better. A coder named Jed McCaleb built Ripple as a better bitcoin. Then he built Stellar as a better Ripple. And he's not the only one.

Now, there's a movement to create a technology that would let all these online ledgers talk to one another, that would let you send money between these systems. Dubbed the "interledger protocol," the project began at the company that oversees Ripple. But in recent months, after the company publicly shared the idea, it has also won the support of several other notable names, including Microsoft and the World Wide Web consortium, the organization that sets the technical standards for the web. The idea is to create a single worldwide network that can not only unite all digital currencies, but all companies and individuals who use those currencies.