How a node operates
Receive, verify, store and relay
A Bitcoin node constantly exchanges information with other nodes. It receives transactions, blocks and network messages, then checks whether they follow Bitcoin’s rules.
The node does not trust the sender. Every piece of information must pass verification before it is accepted into the node’s local view of Bitcoin.
Valid information may be stored and shared with peers. Invalid information is rejected.
Peer-to-peer
Bitcoin nodes communicate directly with one another rather than through a central server.
Independent verification
Each node checks information for itself instead of trusting another participant.
Rule enforcement
Invalid transactions and blocks are rejected automatically by the node.
Data relay
Valid transactions and blocks are shared with connected peers.
Node workflow
From transaction broadcast to verified block
A node performs a repeated cycle of receiving, checking and sharing data.
Connect to peers
Your node connects to other Bitcoin nodes across the peer-to-peer network.
Receive transactions
Peers send your node transactions that have been broadcast to the network.
Verify each transaction
Your node checks signatures, inputs, outputs and whether the transaction follows Bitcoin's rules.
Store valid transactions
Valid unconfirmed transactions may be held temporarily in your node's mempool.
Receive a new block
When a miner finds a block, it is broadcast through the network to connected nodes.
Verify the block
Your node checks proof of work, transaction validity, block structure and consensus rules.
Transaction verification
Every transaction must pass the rules
When a transaction arrives, your node checks that it spends real, available bitcoin and that the owner has provided a valid signature.
A transaction that fails these checks is rejected and is not added to the node’s mempool.
Verification checks
The transaction format is valid
The digital signatures are valid
The inputs exist and have not already been spent
The output values do not exceed the input values
The transaction does not create bitcoin from nothing
The transaction follows current consensus rules
Invalid transactions are rejected
A node does not accept a transaction simply because it came from a wallet, exchange, miner or another node.
The mempool
Where valid transactions wait
The mempool is the node’s temporary collection of valid transactions that have not yet been confirmed in a block.
Temporary storage
The mempool stores valid transactions that have not yet been included in a block.
Local to each node
There is no single global mempool. Each node may hold a slightly different set of transactions.
Fee competition
Transactions offering higher fees are often more attractive to miners during busy periods.
Not permanent
Transactions can leave the mempool after confirmation, expiry, replacement or removal.
There is no single global mempool
Each node maintains its own local mempool. Two nodes may temporarily see different transactions because of network timing or local policy settings.
Block verification
A miner’s block is only a proposal
When a miner broadcasts a block, your node checks the entire block before adding it to its verified blockchain.
The block references the correct previous block
The proof of work meets the required difficulty
The block size and weight are within the rules
Every transaction inside the block is valid
The block reward does not exceed the permitted amount
The block timestamp and structure are acceptable
Initial blockchain sync
Verifying Bitcoin from the beginning
The first time Bitcoin Core runs, it downloads and verifies Bitcoin’s blockchain history. This process is called the initial block download.
Download block headers
Your node first learns the structure and order of the blockchain.
Download historical blocks
Blocks are downloaded from peers across the Bitcoin network.
Verify from the beginning
Your node checks the blockchain from Bitcoin's earliest block onward.
Build local databases
Bitcoin Core builds the indexes and transaction records needed for operation.
Reach the chain tip
Once caught up, the node only needs to verify new transactions and blocks.
Archival mode
Keeps historical block files on disk after verification.
Pruned mode
Fully verifies history but deletes older block files to save storage.
Peer communication
How nodes share information
Bitcoin uses a peer-to-peer network. Your node connects directly to other nodes and exchanges transactions, blocks and network information.
Your node
Connected peers
Wider network
Your node does not need to trust its peers
Peers provide information, but your node verifies that information independently. A dishonest peer cannot make your node accept an invalid transaction or block.
Chain selection
How a node chooses the valid chain
A node follows the valid chain with the most accumulated proof of work. It does not simply choose the chain with the greatest number of blocks.
Every block in that chain must still satisfy Bitcoin’s consensus rules.
Common questions
How nodes behave in practice
Does my node trust miners?
No. Miners propose blocks, but your node independently verifies every block before accepting it.
Does my node need to know who sent a transaction?
No. Bitcoin verification depends on cryptographic signatures and transaction rules, not personal identity.
Can two nodes have different mempools?
Yes. Transactions propagate over time, and nodes can use different local policies.
What happens when my node goes offline?
When restarted, it reconnects to peers, downloads the blocks it missed and verifies them.
Can a bad peer corrupt my node?
A peer can send invalid data, but your node checks that data and rejects anything that breaks Bitcoin's rules.
Lesson summary
The important points
Nodes connect directly to other nodes across Bitcoin's peer-to-peer network.
Every transaction is checked before entering the node's mempool.
Every block is independently verified before being added to the blockchain.
Miners propose blocks, but nodes enforce the rules.
Initial sync verifies Bitcoin's history from the beginning.
Pruned nodes still perform full verification.
A node follows the valid chain with the most accumulated proof of work.