A Directed Acyclic Graph (DAG) is a data structure where transactions are linked in a one-directional, non-circular graph rather than grouped into sequential blocks. In DAG-based networks, each new transaction validates one or more previous transactions, allowing parallel processing and theoretically higher throughput than traditional blockchains.
How It Works
In a traditional blockchain, transactions are batched into blocks that form a single linear chain. In a DAG, each transaction is its own unit that directly references and confirms previous transactions. This creates a web-like structure rather than a chain.
The process works as follows:
- A user submits a transaction.
- The protocol requires the transaction to validate two or more previous unconfirmed transactions (called “tips”).
- The new transaction attaches to those tips, forming a directed link.
- As more transactions reference older ones, confidence in those older transactions increases.
Because transactions don’t need to wait for block assembly, DAGs can theoretically process many transactions simultaneously. The network gets faster as activity increases — more participants means more transactions confirming each other.
DAG vs. Blockchain
| Property | Blockchain | DAG |
|---|---|---|
| Structure | Linear chain of blocks | Graph of linked transactions |
| Transaction grouping | Batched into blocks | Individual transactions |
| Consensus | Miners/validators agree on blocks | Transactions validate each other |
| Throughput scaling | Limited by block size/time | Increases with network activity |
| Finality | Block confirmations | Cumulative weight/confidence |
Notable DAG Projects
- IOTA Tangle — designed for Internet of Things microtransactions; uses a coordinator node for security (with plans for full decentralization).
- Hedera Hashgraph — uses a DAG combined with virtual voting and gossip-about-gossip protocol for fast consensus.
- Kaspa — implements a blockDAG (GHOSTDAG protocol), combining block-based mining with DAG parallelism.
- Nano — uses a block-lattice structure (each account has its own chain), a DAG variant enabling feeless transactions.
History
- 2015 — Sergio Demian Lerner publishes “DAGCoin,” proposing a DAG-based cryptocurrency without blocks.
- 2016 — IOTA Foundation launches the Tangle, the first major DAG-based distributed ledger.
- 2018 — Hedera Hashgraph launches mainnet, combining DAG structure with BFT consensus.
- 2021 — Kaspa launches with the GHOSTDAG protocol, introducing proof-of-work block-DAG architecture.
Common Misconceptions
“DAGs have completely replaced the need for blockchains.”
DAG-based systems solve certain scalability problems but introduce their own challenges — particularly around security at low network activity. Most DAG projects have required centralized coordinators or additional consensus layers during early stages. Blockchains remain dominant for smart contract platforms and DeFi.
Social Media Sentiment
DAG projects attract enthusiasts who see them as the “next evolution” beyond blockchains. IOTA and Hedera communities are vocal about throughput advantages, though critics point out that centralization trade-offs (like IOTA’s coordinator) undermine the decentralization narrative. Kaspa has gained attention for combining DAG with proof-of-work mining.
Last updated: 2026-04
Related Terms
Sources
- IOTA Foundation — The Tangle — technical overview of the IOTA DAG architecture.
- Hedera — Hashgraph Consensus — explanation of DAG with gossip protocol.
- Kaspa — GHOSTDAG Protocol — blockDAG implementation documentation.
- Lerner, S.D. — DAGCoin Draft (2015) — the original DAG cryptocurrency proposal.
- Investopedia — Directed Acyclic Graph — general explanation of DAGs in crypto.