What Happens When You Send Bitcoin
No bank, no clearing house, no settlement day. Instead: a waiting room, a lottery, and ten minutes of cryptographic ceremony.
The walkthrough
Sending Bitcoin feels like sending an email, but underneath there is no bank moving your balance and no clearing house netting it off. There is a public ledger that thousands of computers each hold a copy of, and your payment is just a request to all of them: *"please agree that these coins now belong to that address."*
Signing, not sending. Your wallet doesn't move money, it builds a transaction that names which earlier coins (UTXOs, unspent transaction outputs) you're spending and where they should go. It then signs that with your private key. The signature proves you own the coins without revealing the key. Crucially, a Bitcoin transaction has no "amount left over" field: if you spend a 1 BTC coin to pay 0.3 BTC, you must explicitly send 0.7 BTC back to yourself as change, or the rest is lost to fees.
The waiting room. Once broadcast, your transaction sits in the mempool, a holding area every node keeps of valid-but-unconfirmed transactions. It is *not yet settled*. Miners pick which transactions to include next, and they pick by fee rate (satoshis per virtual byte), not by who asked first. Pay a low fee when the network is busy and you can wait hours; pay too low and you may be dropped entirely.
The lottery. Roughly every 10 minutes, one miner wins the proof-of-work race, guessing a hash that meets the network's difficulty target, and earns the right to publish the next block (~1–4 MB of transactions). Winning is probabilistic, like a lottery weighted by computing power; that 10-minute average is enforced by difficulty adjustments every 2,016 blocks. The winner collects the block reward (newly minted bitcoin) plus all the fees inside their block.
Confirmations, not finality. When your transaction lands in a block it has 1 confirmation. Each later block stacked on top adds another. Exchanges often wait for 3–6 confirmations (~30–60 minutes) because a very recent block can be orphaned if two miners find blocks at once and the network later picks the longer chain. Bitcoin offers *probabilistic* settlement: the deeper your transaction is buried, the more economically impossible it becomes to reverse.
Failure modes that surprise newcomers: a fee too low to ever confirm (rescuable with RBF or CPFP), sending to the wrong address (irreversible, no chargebacks), and forgetting that the network confirms *coins*, not *people*: there is no name, no bank, and no one to call.
The rail map
The journey of one transaction
- 1Wallet signs
Your wallet selects UTXOs and signs the transaction with your private key, no money has moved yet.
- 2Broadcast
The signed transaction is gossiped to peer nodes, which validate it and relay it onward.
- 3Mempoolwhere value leaks
It waits, unconfirmed, in every node’s mempool, ranked by the fee rate you chose.
- 4Mining lotteryhighest cost / risk
Miners race proof-of-work; the winner builds a block, favouring the highest-fee transactions.
- 5Block published
~Every 10 minutes a block is added; your transaction now has 1 confirmation.
- 6Confirmations
Each later block deepens it; 3–6 confirmations make a reversal economically impossible.
Glossary
UTXO
An unspent transaction output, a discrete chunk of bitcoin you received and can now spend whole. Wallets combine them like coins and notes.
Mempool
The pool of valid but unconfirmed transactions each node holds while they wait to be mined.
Fee rate
Fee per unit of transaction size (satoshis per virtual byte), what miners actually rank by, not the total fee or who paid first.
Proof-of-work
The computational lottery in which miners burn electricity hashing until one finds a valid block, earning the right to extend the chain.
Confirmation
One block built on top of the block containing your transaction; more confirmations mean a deeper, harder-to-reverse settlement.
Change
The leftover bitcoin a transaction must send back to your own wallet, since a UTXO must be spent in full.
Check yourself
1.You broadcast a Bitcoin transaction and it appears in the mempool. Has the payment settled?
2.The network is congested and your transaction is stuck for hours. What is the most likely reason?
3.You spend a single 1 BTC coin to pay someone 0.3 BTC. Where do the other 0.7 BTC go?
4.Why do exchanges typically wait for 3–6 confirmations before crediting a deposit?
5.You accidentally send bitcoin to the wrong (but valid) address. What can you do?