How Bitcoin Transactions Work: From Send to Final Confirmation

Bitcoin doesn't track account balances — it tracks coins as discrete chunks called UTXOs (unspent transaction outputs). Your wallet's 'balance' is the sum of UTXOs your keys control. When you send 0.3 BTC, your wallet selects UTXOs that cover it (say a 0.5 BTC chunk), creates one output to the recipient and a second 'change' output back to yourself — exactly like paying a $30 bill with a $50 note.

Authorization is pure cryptography: your wallet signs the transaction with your private key, producing a signature anyone can verify against your public key but nobody can forge. The key never leaves your device — that's why a hardware wallet can authorize transactions from an infected computer safely. The signed transaction broadcasts to nodes, lands in the mempool, and waits for a miner to include it based on the fee you attached.

Inclusion in a block is the first confirmation; each block built on top adds another. Reversal would require redoing the proof-of-work for that block plus everything after it, faster than the honest network extends the chain — which is why one confirmation is fine for coffee, exchanges typically wait for one to three, and six has been the conservative standard for large sums since Bitcoin's earliest days. Once buried, a transaction is as final as money movement gets.