What happens when you press Send?
There is no bank approving a Bitcoin payment. Your wallet prepares a transaction, independent participants verify it, and confirmations make the payment increasingly trusted over time. This lesson follows that journey from the Send button to a confirmed record.
Learning objectives
- Explain what happens after pressing Send.
- Describe how wallets create transactions.
- Explain how nodes verify transactions.
- Define the mempool.
- Explain why fees exist.
- Describe confirmations and finality.
- Identify common misconceptions.
Creating a transaction
A wallet selects spendable bitcoin, creates outputs for the recipient and change when applicable, estimates a fee, and signs the proposed transaction with private keys. A digital signature proves authorisation using public information without revealing the key itself. The transaction is then ready for broadcast.
The exact timing and route can vary. This diagram shows the usual high-level path of a valid transaction.
Broadcast and node verification
After broadcast, nodes independently check whether the transaction follows Bitcoin's rules. They check valid signatures, spendable inputs, proper format, protocol compliance, and attempts at invalid double spending. Nodes reject transactions that fail these checks. Learn more about this role in Bitcoin Nodes.
What is the mempool?
Mempool means memory pool. It is a temporary holding area where valid unconfirmed transactions may wait before a block includes them. Different nodes can have slightly different mempool contents, and appearance there is not a confirmation.
Mining and confirmations
Miners select transactions from the mempool for blocks with limited capacity. Inclusion gives a transaction its first confirmation. Later blocks build on that history, so confidence increases as confirmations accumulate. Mining and consensus are explored in their dedicated lessons.
Fees, block space, and finality
Fees compete for limited block space and generally relate to transaction characteristics rather than the bitcoin value sent. Network demand changes fee estimates, and wallets often estimate them automatically. A higher fee may influence priority but does not guarantee a time. Bitcoin finality is probabilistic rather than absolute: reversing confirmed history becomes increasingly difficult as valid blocks accumulate.
A practical example
Alice sends bitcoin to Ravi. Her wallet creates and signs the transaction, then broadcasts it. Nodes verify it and may keep it in their mempools. A miner includes it in a block, giving Ravi a first confirmation. As later blocks arrive, Ravi sees additional confirmations. Ravi cannot alter Alice's authorised transaction, and neither party should assume an identical confirmation time for every payment.
Common misconceptions
Broadcast, block inclusion, and confirmations are separate stages.
Miners propose blocks; nodes independently validate rules.
Fees usually relate to demand and transaction characteristics.
Valid authorisation and node checks prevent simple modification.
Timing varies with network conditions and block inclusion.
Key Takeaways
Wallets create and sign transactions.
Signatures authorise spending without exposing private keys.
Nodes verify transactions before accepting them.
The mempool holds valid unconfirmed transactions temporarily.
Miners include transactions in blocks.
Fees compete for limited block space.
Confirmations increase confidence over time.
Review address, amount, and fee before sending.
Quick Quiz
Question 1 of 4
Who creates a Bitcoin transaction before broadcast?
Frequently asked questions
Why is my transaction pending?
A valid transaction may be waiting in node mempools for a miner to include it in a block.
What is the mempool?
It is a temporary collection of valid unconfirmed transactions that nodes may keep in memory.
Can I cancel a Bitcoin transaction?
After broadcast or confirmation, cancellation is not generally guaranteed. Review details carefully before sending.
Do higher fees always make confirmations faster?
Higher fees can influence priority when block space is scarce, but they do not guarantee a confirmation time.
How many confirmations are enough?
It depends on the situation and risk involved; there is no universal number for every payment.
Can someone change my transaction after I send it?
Nodes verify authorisation and transaction rules. A recipient cannot simply modify an authorised transaction.
Next: Bitcoin Nodes
Continue to learn how independent nodes validate the rules behind each transaction and block.
Continue to Bitcoin NodesContinue Learning
Explore the next ideas connected to this topic.
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