# What does nonce do in Ethereum?

> Understanding the critical role of nonce in Ethereum transactions and how it maintains transaction order

Source: https://www.rohandey.com/writings/what-does-nonce-do-in-ethereum  
Published: 2021-11-27  
Updated: 2021-11-27  
Category: Crypto

Ethereum is a decentralized network of nodes. When you send a transaction to the Ethereum blockchain, it gets sent into the mempool until some miner mines it and includes it in a valid block.

Suppose you want to send two transactions transferring **3 ETH** and **6 ETH** respectively and want them to be processed sequentially. You would not wait after sending one transaction till it gets mined and included in a block. Instead, you would send out both transactions one after the other.

The **nonce** is one of the **most critical** and **least understood** components of an ethereum transaction.

An **ethereum** **transaction** is composed of the following components:

* **nonce** - Number of confirmed transactions this account has previously sent
* **gasPrice** - Price of gas (in wei) the originator is willing to pay for this transaction
* **to** - Recipient of this transaction (smart contract or EOA)
* **value** - How much ether this transaction is sending
* **data** - Any binary data payload
* **v,r,s** - Three components of ECDSA signature of originating account holder

As explained in the Ethereum Yellow Paper, a nonce is defined as:- 

> A scalar value equal to the number of transactions sent from this address or, in the case of accounts with associated code, the number of contract-creations made by this account.

Without a **nonce**, it would be impossible for miners to know your intent to **maintain the order of transactions**.

However, with the nonce, if your first transaction (**3 ETH**) has **nonce 0** (assuming it's a new account), then **6 ETH** transactions will have **nonce 1.** Now, the transaction with **6 ETH** would not be processed unless the previous transaction of **3 ETH** (with lower nonce) is processed. Hence, maintaining the sequence of transactions.

If there are **gaps in nonces**, all subsequent transactions sit in the **mempool**, waiting for the gap to be **filled.**

For example: if the total transaction confirmation count for account **X is 8 (nonce = 8)**, and a transaction with (**nonce = 10)** from account X is broadcasted to the network, it will sit in **mempool** till another transaction from account X with (**nonce = 9)** is broadcasted and mined. Thus, filling the gap.