Transaction
A serialized state transition that a blockchain can validate, relay, and include in a block.
A transaction proposes a change to blockchain state. Most user transactions include cryptographic authorization, but the exact structure depends on the protocol; a proof-of-work coinbase transaction, for example, creates the permitted block subsidy without an ordinary sender signature.
In a UTXO system, a transaction consumes named outputs and creates new outputs. In an account system, it commonly changes balances, nonces, and contract storage. Nodes independently check the applicable consensus and local relay rules.
A relayed transaction may enter a node's mempool before a miner includes it in a block. Inclusion gives it one confirmation; later blocks increase the cost of reorganizing that history. Unconfirmed transactions can be dropped, conflicted, or replaced according to network policy.
Related terms
Explore connected entries beyond the alphabetical index.
Mempool
→A node's local set of unconfirmed transactions accepted for possible relay and block inclusion.
Block
→A batch of valid transactions added to a blockchain, linked to the previous block by a cryptographic hash.
Confirmations
→The count of blocks confirming a transaction, usually including the block that first contains it.
Transaction Fee
→The amount paid to miners or validators for including a transaction and consuming scarce block space or execution resources.
Unspent Transaction Output (UTXO)
→A discrete spendable output on a UTXO blockchain, similar to a digital coin that must be spent whole.