Ethereum is a world computer: a globally shared infrastructure existing across thousands of interconnected networks. Users interact with Ethereum through wallets like MetaMask, which create and send transactions to the network. Once received, these transactions are recorded in blocks.
The Anatomy of an Ethereum Transaction
Every Ethereum transaction consists of three key components:
- Metadata: Includes ETH transfer details, gas information, and signature data.
- Cache: Lists accounts and private keys the transaction will use.
- Data: The payload (smart contract code or API call).
Metadata: Transaction Essentials
Here's what makes up the metadata in an Ethereum transaction:
- ChainID: Protects against replay attacks (introduced by EIP-155).
- Type: Two main types - new contracts (0x0) and all others (0x2).
- Nonce: Count of transactions sent from a specific address.
- To: Recipient address (wallet or smart contract).
- Value: Amount of ETH being transferred.
- Gas: Units of gas used for the transaction.
- MaxFeePerGas: Maximum fee per gas unit a user is willing to pay.
- MaxPriorityFeePerGas: Additional tip for miners/validators.
- (r, s, v): Signature values verifying transaction authenticity.
👉 Learn more about Ethereum gas fees
Cache: Access Lists
The cache includes an accessList - addresses and private keys the transaction will use. Introduced by EIP-2929, this allows clients to prefetch data, currently offering a 10% discount on access costs.
Data: The Transaction Payload
Transaction data comes in three forms:
- ETH Transfers: Blank data field
- Smart Contract Calls: Function names and parameters
- New Contracts: Entire contract code
This binary data isn't part of EVM state but provides temporary information for contracts during execution - a feature leveraged by rollups for cost-efficient data storage.
Why Hashes Matter in Ethereum
Hashing converts arbitrary data into fixed-size values. Key benefits:
- Cannot be reversed
- Produces uniform output lengths
- Essential for Ethereum's security
Frequently Asked Questions
What's the difference between gasPrice and maxFeePerGas?
GasPrice was the traditional pricing model, while maxFeePerGas is part of Ethereum's newer EIP-1559 fee structure that includes base fees and priority tips.
How does the accessList save money?
By declaring needed resources upfront, transactions get a 10% discount on accessing those specific items compared to undeclared accesses.
Can transaction data be changed after submission?
No - once broadcast, transaction data is immutable. Miners/validators may choose whether to include it in a block, but cannot alter its contents.
Ethereum transactions form the backbone of all network activity - from simple ETH transfers to complex smart contract deployments. Understanding their structure helps users navigate the blockchain more effectively while optimizing costs and security.
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