Deciphr Academy
Track 1 · Module 5 · Lesson 1 of 6 · 5 min read

What is inside an Ethereum transaction?

Short answer

A transaction is a signed instruction from an account, such as "send 1 ETH to this address".1 Besides the receiver and the amount, it carries a counter called the nonce and the most you will pay in fees.1

Transactionfromyour addresstothe receivervalueETH to senddataoptionalnonceits numbergas limitmost gasmax feeper unit of gastipper unit of gassignatureyour keysendPending poolwaitingpickedBlockby a validatorThe fee comes out ofyour ETH balanceSigned, sent, queued, included
Fig. 1. A transaction is a signed form. It waits in a pool until a validator puts it in a block.

A signed instruction

On Ethereum, a transaction is a signed instruction from an account.1 The simplest one moves ETH from one account to another.1

A transaction is started by an account that a person controls, not by a smart contract.1 It must be signed with the sender's private key. The signature proves it came from the sender and was not faked.1

The fields

Every transaction is a short form with set fields.1 The names below are the ones developers use.

Field What it holds
from The sender's address.1
to The receiver. If the receiver is a contract, the transaction runs the contract's code.1
value How much ETH to send, counted in wei. 1 ETH is a billion billion wei.1
data Optional extra information, used when calling a contract.1
nonce A counter: this transaction's number from the account.1
gasLimit The most units of gas the transaction may use.1
maxPriorityFeePerGas The most you will tip the validator, per unit of gas.1
maxFeePerGas The most you will pay per unit of gas, base fee and tip included.1
signature Made with the sender's private key, it shows the sender approved it.1
What comes next

Lesson 2 explains gas and gwei. Lesson 3 explains the base fee, the tip and the max fee. Lesson 4 explains the nonce.

Three kinds of transaction

  • A regular transaction moves ETH from one account to another.1
  • A contract deployment has no "to" address. Its data field holds the new contract's code.1
  • A contract call sends the transaction to a smart contract's address.1

Asking a contract a question that changes nothing is different. That kind of read-only call costs no gas.1

What happens after you press send

  1. A transaction hash is created. It works like a receipt number you can look up on an explorer.1,2
  2. The transaction is sent to the network and joins a pool of other pending transactions.1
  3. A validator picks it and puts it in a block.1
  4. Over time the block is marked as justified, then finalised, which makes it far harder to change.1

Once a transaction is in a block, it can't be cancelled or replaced.2

Where the fee comes from

The fee comes out of the ETH left in your account, not out of the amount you send.3 Both leave your account in the same single transaction.3 Fees on Ethereum are always paid in ETH, even when you send a token.4,3

Transaction types

Ethereum has several transaction formats. The original one is called type 0, or "legacy".1 Type 2 came with EIP-1559, an Ethereum Improvement Proposal. It splits the fee into a base fee and a priority fee, and is now the standard.1,5 Type 3 carries "blobs" of data, mainly for layer 2 networks.1

Our viewRead the "to" address and the amount slowly before you sign. Your wallet can fill in the fee fields, but only you know where the money should go.
Sources
  1. Transactions. ethereum.org developer docs, page updated 7 October 2026.
  2. How to replace a Pending/Dropped transaction. Etherscan Information Center, 25 November 2021, updated 21 June 2026.
  3. What is Gas Fee?. Etherscan Information Center (Kaven Choi), 26 November 2019, updated 21 June 2026.
  4. Gas fees. ethereum.org, page updated 8 April 2025.
  5. EIP-1559: Fee market change for ETH 1.0 chain. Ethereum Improvement Proposals (Vitalik Buterin and others), created 13 April 2019, status Final.
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General education built from the publicly available sources listed above. Not financial, legal, tax or investment advice. Naming a company, project or regulator is not an endorsement either way. Last checked 2026-10-22. Terms and disclaimer.