Nonce - What is it and optional use

In blockchain technology, the nonce is a transaction counter that helps to prevent double-spending and replay attacks on a blockchain network. This value is attached to each Ethereum and EVM-compatible chain sender address.

Ethereum and other EVM-compatible blockchains require the nonce value for each transaction to ensure that the same transaction is not executed twice and that no one can replay a previously sent transaction.

With Tatum, when the nonce is not specified when making a transaction on Ethereum and other EVM-compatible chains, our Engine automatically adds it based on the sender's address.

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The Tatum engine has a delay when automatically calculating the nonce. Users with a high transaction broadcast volume should use a manual nonce value. Otherwise, errors about "replacement transaction" will be common.

Finding the nonce value

v3 REST API

You can get the current nonce value for their Ethereum sender address by making an API call.

• Endpoint: https://apidoc.tatum.io/tag/Ethereum#operation/EthGetTransactionCount

Example:

curl --location 'https://api.tatum.io/v3/ethereum/transaction/count/0x271ebc3C939Db4d0######' \
--header 'x-api-key: {Mainnet_API_KEY}'
//response:
4887 // Current nonce value in decimals

RPC node request

You can also get the current nonce value using an Ethereum node's RPC call.

Example:

curl --location 'https://api.tatum.io/v3/blockchain/node/ETH/' \
--header 'x-api-key: {Mainnet_API_KEY}' \
--header 'Content-Type: application/json' \
--data '{
    "jsonrpc":"2.0",
    "method":"eth_getTransactionCount",
    "params":[
        "0x271ebc3C939Db4d0######'",
        "latest"
        ],
    "id":1
    }'
//response:
{
    "jsonrpc": "2.0",
    "id": 1,
    "result": "0x1316" //needs conversion to decimal
}

Nonce value and dropped transactions

Single transaction

If a transaction with nonce value X is dropped or doesn't get included in a block, the nonce value for that account doesn't increase. The nonce is only increased once a transaction is successfully included in a block.

Multiple transactions

If you try to send multiple transactions at the same time, each transaction must have nonce+1, nonce+2, nonce+3, nonce+4, etc. If for some reason the transaction with nonce+2 gets dropped (low gas price, network congestion, etc.), the transactions with values nonce+3 and nonce+4 will be stuck in the mempool and won't be mined until the transaction with nonce+2 is mined.

To solve this, you would need to re-send the transaction with nonce+2 with enough gas for it to be mined. Once the transaction with nonce+2 would be mined, any subsequent transactions with higher nonce value should be able to be mined too.