Directed Acyclic Graph (DAG)

A directed acyclic graph, or DAG, is a data structure in which records point only to earlier records and never form a loop. Some crypto networks use a DAG instead of a single chain of blocks: each new transaction references and confirms one or more previous transactions, so many transactions can be added in parallel rather than waiting for the next block. Supporters argue this raises throughput and lowers fees, while critics point out that DAG designs still need their own mechanisms to agree on transaction ordering and prevent double spending. IOTA's Tangle and Hedera's hashgraph are the most frequently cited examples. Understanding a DAG matters mainly because it changes how confirmation, finality and fees behave compared with a conventional blockchain.