Nonce

Transactions signed by the same private key (i.e., with the same address) are submitted and handled in an order using nonce. Usually, nonce is a non-negative integer value, starting from 0, that stands for the number of transactions accepted to blocks so far. Whenever a transaction is submitted its nonce is check in the following way:

  • If the nonce value is equal to (the number of transactions with the same address in blocks) + 1, it's accepted

  • Otherwise, it's kept in pending mode with a predefined timeout value until the condition met.

We call this type of nonce strictly ordered nonce. This is enough for typical human-generated transactions. For more use cases like machine-generated transactions, we support two more types: loosely ordered nonce and unordered nonce.

Transactions with loosely ordered nonce are ordered using timestamp:

  • If the timestamp is larger than the last timestamp, it's accepted

  • Otherwise, it' rejected

Transactions with unordered nonce is always accepted unless a transaction with the same transaction hash is already in blocks.

Three different types of nonce can be compared as follows:

Type

Nonce Field

When To Use

Good For

API Version

Strictly ordered

Non-negative integer

Single client

Human-generated txs

1.0

Loosely ordered

-1

Multiple clients, transactions are aligned with time

Machine-generated txs with multiple clients

TBD

Unordered

-2

Single or multiple clients, transactions are not aligned with each other.

Machine-generated txs with different generation time and submission time

1.0

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