How a Bitcoin payment goes from your wallet to the blockchain: signing, checking, waiting in the mempool, mining and confirmation, step by step.
The five steps
- You create a transaction. Your wallet writes a message like "move 0.01 BTC from my coins to this address" and signs it with your private key.
- The network checks it. Your wallet sends it to nodes. Each node checks the signature and makes sure the coins haven't already been spent.
- It waits in the mempool. Valid transactions wait in each node's mempool until a miner picks them up.
- A miner puts it in a block. Miners bundle waiting transactions into a block and compete to find a valid Proof of work. Higher fees usually get picked first.
- The block joins the chain. Every node checks the new block and adds it to its copy of the blockchain. Your payment now has one confirmation.
Why can't anyone cheat?
- You can't spend someone else's coins, because you can't produce their signature.
- You can't spend your coins twice, because every node rejects a transaction whose coins are already spent. See the The double-spending problem.
- You can't rewrite history cheaply, because changing an old block means redoing all the work on top of it.
The three ingredients
Bitcoin combines three older ideas in a new way:
- Digital signatures prove who may spend coins. See Digital signatures.
- A peer-to-peer network spreads payments with no central server. See The peer-to-peer network.
- Proof of work makes the shared history expensive to rewrite. See Proof of work.
None of them alone solves money without a bank. Together they let strangers agree on one history of payments.
What happens when things go wrong
- Two people mine a block at once: nodes briefly disagree, then all follow the longer chain. See Stale blocks and chain reorganizations.
- Someone broadcasts an invalid payment: validating nodes reject transactions that break their consensus rules.
- Fees are too low: the payment waits until block space frees up, or you can bump it. See Replace-by-fee (RBF).
Watch it happen
Every step above is visible on MyBitcoinExplorer: unconfirmed payments on the mempool page, and their confirmation when they appear in the latest blocks.
Key takeaways
- A transaction is signed by your wallet, checked by nodes, then added to a block by a miner.
- Every node independently enforces the same rules.
- Proof of work makes rewriting history expensive.
Common questions
How long does a Bitcoin payment take?
It reaches the network in seconds. The first confirmation comes when the next block is mined, about 10 minutes on average, depending on the fee you paid.
Who checks that a payment is valid?
Every full node checks every transaction and block for itself, using the same consensus rules.
Does Bitcoin need the internet?
Nodes and wallets normally use the internet, but the protocol only needs some way to pass messages. Blocks have even been broadcast by satellite and radio.
What happens if the internet goes down in one country?
The rest of the network keeps working. When the country reconnects, its nodes download the blocks they missed and catch up.