IOTA is the cryptocurrency project that uses a directed acyclic graph called the Tangle as its ledger.
Unlike a conventional blockchain, the Tangle is designed as a network of transactions arranged in a directed acyclic graph rather than a single chain of blocks. In IOTA’s original design, a new transaction was expected to approve earlier transactions, linking activity together without relying on miners in the same way as Bitcoin.
IOTA was founded in 2015 by David Sønstebø, Sergey Ivancheglo, Dominik Schiener, and Serguei Popov. Its stated focus was machine-to-machine payments and the Internet of Things, where devices could exchange small amounts of value or data.
The Tangle is often confused with a blockchain because both are distributed-ledger technologies. IOTA’s architecture is distinctive, but its implementation and consensus design have changed over time, so descriptions of the project should distinguish its Tangle ledger from ordinary linear blockchains.