How Transactions Work

Introduction

Transactions are the fundamental unit of execution in the Stacks blockchain. Each transaction is originated from a Stacks account, and is retained in the Stacks blockchain history for eternity. This guide helps you understand Stacks transactions.

Lifecycle

Transactions go through phases before being finally confirmed, and available for all, on the Stacks 2.0 network.

• Generate: Transactions are assembled according to the encoding specification.

• Validate and sign: Transactions are validated to confirm they are well-formed. Required signatures are filled in.

• Broadcast: Transactions are sent to a node.

• Register: A miner receives transactions, verifies, and adds them to the "mempool," a holding area for all the pending transactions.
• Process: Miners review the mempool and select transactions for the next block to be mined. Depending on the transaction type, different actions can happen during this step. For example, post-conditions could be verified for a token transfer, smart-contract defined tokens could be minted, or an attempt to call an existing smart contract method could be made.

• Confirm: Miners successfully propose blocks with a set of transactions. The transactions inside are successfully propagated to the network when the stackers approve them.

A transaction can have one of three states once it is registered: pending, success, or failed.

Types

Stacks supports a set of different transaction types:

Type	Value	Description
Tenure change	TenureChange	A tenure change is an event in the existing Stacks blockchain when one miner assumes responsibility for creating new stacks blocks from another miner. A change in tenure occurs when a Stacks block is discovered from a cryptographic sortition. Carried out by stackers.
Tenure change block found	TenureChange-BlockFound	A TenureChange-BlockFound transaction is induced by a winning sortition. This causes the new miner to start producing blocks, and stops the current miner from producing more blocks.
Tenure change extend	TenureChange-Extend	A TenureChange-Extend, which is induced by Stackers, resets the current tenure's ongoing execution budget, thereby allowing the miner to continue producing blocks.
Token transfer	token_transfer	Asset transfer from a sender to a recipient
Contract deploy	smart_contract	Contract instantiation
Contract call	contract_call	Contract call for a public, non read-only function

A sample of each transaction type can be found in the Stacks Blockchain API response definition for transactions.

Read-only contract call calls do not require transactions. Read more about it in the network guide.