Transaction
Web3 / blockchain technology
A signed instruction broadcast to a blockchain network that records the transfer of value or execution of a smart contract function, permanently added to the blockchain once validated by the network. Every blockchain transaction contains at minimum: a sender address, recipient address or contract, value amount, a nonce (to prevent replay), a digital signature proving the sender authorized it, and fee data. Transactions in smart contract platforms like Ethereum can also include calldata encoding which function to call and with what parameters. Transactions are first broadcast to the mempool, where they await inclusion in a block by validators or miners who prioritize them based on the fee offered. Once included in a block that achieves finality, the transaction becomes irreversible on the canonical chain. Example: Sending 1 ETH from wallet A to wallet B is a simple value transfer transaction. Interacting with a Uniswap pool to swap tokens is a transaction that includes calldata triggering a specific swap function in Uniswap's smart contracts. Why it matters for Web3: Transactions are the atomic unit of activity on any blockchain—every DeFi trade, NFT mint, token transfer, and governance vote is executed as one or more blockchain transactions. Understanding how transactions are structured, priced, and finalized is foundational to using or building on any blockchain network.
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