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ELI5 IOTA Tangle

IOTA Tangle Illustration by Tiagodimas2 via Wikimedia CC BY 2.0

In a previous article, we’ve discussed the concept of a DAG – Directed Acyclic Graph.

In this post we talk about a DAG application in the IOTA ecosystem – the IOTA Tangle.

As you may have guessed from the Wikipedia illustration at the top of this article, a tangle looks like a graph of transactions.

At first look it might seem like a messy spiderweb, but it’s actually a special graph that moves only one way. (For details about this see the aforementioned DAG post).

IoT Tangle

IOTA works like this because it’s designed for IoT – Internet of Things. So each little device in a mesh of thousands, perhaps millions, of devices must be able to swiftly send and receive transactions.

If each IOTA node employed a rigid blockchain data structure like Bitcoin, there’d need to be a more rigid synchronization mechanism among all these small scale devices.

In IOTA there’s no need to reach consensus for a single block every X seconds or minutes. Instead, each device must verify two previous parent transactions. Then it makes those TX’s “parents” of a new TX.

If the previous TX’s are valid and they also validate the present one, it guarantees that the next TX’s must also be valid.

By building a graph of relations this way, we end up with a data structure that looks like this:

IOTA Tangle Illustration By Navinram CC BY 2.0 via Wikipedia

You may think of an IOTA Tangle as multiple blockchains moving in parallel. (Blockmesh shares a similar concept.)

Staying Slim

Every network participant must verify 2 previous transactions before they issue one TX. This guarantees that the DAG will stay slim and not too many branches will grow outwards instead of forward.

If you didn’t constrain the system to two TX’s required to verify a next one, you could end up with several independent blockchains growing in various directions.


The IOTA Tangle is IOTA’s decentralized ledger.

It’s represented in a computer program via a well known data structure called a DAG. Several projects use DAG’s instead of linear blockchains.

Since IOTA was designed for large swarms of small scale devices on the Internet of Things, its ledger must be dynamic, very decentralized and lightweight. The IOTA Tangle is designed to meet these requirements.


Neat 3D Visualization of IOTA Tangle

Iota Tangle: A cryptocurrency to communicate Internet-of-Things data

IOTA Wikipedia Entry

An IOTA explorer called Tangle

Both Tangle DAG images credit: Wikimedia Commons

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