How do you read a Bitcoin transaction on a block explorer?
A Bitcoin transaction lists inputs, which spend earlier outputs, and outputs, which create new amounts.1 There is no fee field: the fee is the inputs minus the outputs, and one output is often change going back to the sender.2
Inputs and outputs, not balances
Bitcoin doesn't store account balances. A wallet's "balance" is really the sats waiting in its unspent outputs.1 Every transaction has at least one input and one output.1 Each output waits as an unspent transaction output (UTXO) until a later input spends it.1 Module 3 explains UTXOs.1
Mastering Bitcoin compares a transaction to a line in a double-entry ledger: inputs on one side spend funds, and outputs on the other side receive them.2 An explorer lets you follow these flows from one transaction to the next.2 Each input points back to the output it spends, using that earlier transaction's ID (txid) and the output's position in it.1
Amounts can be counted in satoshis, or sats. There are 100,000,000 sats in 1 bitcoin.3
Spotting change
Inputs work like banknotes: they can't be partly spent.2 So many transactions have a change output that pays the leftover back to the sender.2
To the Bitcoin protocol, a change output and a payment output are exactly the same.2 For privacy, change often goes to a brand-new address of the sender's.2 So an explorer showing two outputs can't tell you for sure which one is the payment. The sender can tell, because the change address belongs to the sender's own wallet.2
The fee is a gap
No line on a Bitcoin transaction says "fee". The fee is the difference between what the inputs bring in and what the outputs pay out.2 The whole value of the inputs must go either to the outputs or to the miner as a fee.1
The fee a transaction needs depends on its size and on the going fee rate, not on the amount sent. mempool.space explains that size comes from things like how many inputs and outputs it has, that bigger transactions pay more, and that fee rates change all the time.4 Module 3 explains fee rates.4
Confirmations
Each block added on top of a transaction gives it one more confirmation.5 The block that holds the transaction counts as the first.2
| Confirmations | What the Bitcoin developer guide says |
|---|---|
| 0 | Sent out but not yet in any block. Generally not to be trusted without a risk check.5 |
| 1 | In the latest block. The risk of a double spend falls sharply, but is still real.5 |
| 6 or more | What software handling high-value or risky payments should wait for before treating a payment as accepted. The guide calls the number "somewhat arbitrary".5 |
Confirmations = the latest block number − the transaction's block number + 1.
Once confirmed, Bitcoin payments can't be reversed. Bitcoin.org says only the person who received the money can refund it.3
mempool.space adds a calming point: a Bitcoin transaction always either confirms completely or not at all. With its transaction ID, you can always see where the money is.4
- Transactions (Bitcoin Developer Guide). Bitcoin Developer Documentation (developer.bitcoin.org).
- Mastering Bitcoin, 3rd edition, chapter 2: How Bitcoin Works. Andreas M. Antonopoulos and David A. Harding (CC BY-SA 4.0), GitHub, December 2023.
- Frequently Asked Questions. Bitcoin.org.
- Mempool FAQ. mempool.space (open-source block explorer).
- Payment Processing: Verifying Payment (Bitcoin Developer Guide). Bitcoin Developer Documentation (developer.bitcoin.org).
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.