Nodes and the network
Nodes, peers, the mempool, consensus rules and how Bitcoin upgrades.
What is the Bitcoin mempool?
The mempool is each node's waiting room for valid transactions not yet in a block. Learn how it works, why it fills up and how to read it live.
What is a Bitcoin node?
A Bitcoin node is a computer that checks every block and transaction against the rules. Learn what nodes do, why to run one and what it takes.
Full nodes vs pruned nodes
A pruned node verifies everything an archival node does, then deletes old blocks to save disk space. Compare both and choose the right one.
The peer-to-peer network
Bitcoin nodes connect to a handful of peers and pass on new transactions and blocks, so news spreads worldwide in seconds. Learn how gossip works.
Initial block download (IBD)
A new Bitcoin node must download and verify every block since 2009 before it is caught up. Learn what initial block download involves and how to speed it up.
Consensus rules
Consensus rules decide what makes a Bitcoin block or transaction valid. Every node enforces them, and a block that breaks one is rejected. See examples.
Relay policy and standardness
Nodes apply extra rules about which transactions they relay and keep in their mempool. Learn how policy differs from consensus and why it matters.
Soft forks and hard forks
A soft fork tightens Bitcoin's rules so old nodes keep working; a hard fork loosens them so old nodes reject the new chain. Learn the difference.
Bitcoin Improvement Proposals (BIPs)
BIPs are design documents proposing changes or standards for Bitcoin. Some change consensus; many just help wallets work together. See the key ones.
SPV and light clients
Light (SPV) clients download only block headers and check merkle proofs, trusting the most-work chain instead of verifying every rule. Learn the trade-offs.
Transaction indexes versus address-history indexes
See why a synced Bitcoin node may find blocks but need a separate index for transaction IDs, address history or complete explorer reports.
Keep Bitcoin Core RPC private
Learn why Bitcoin Core RPC is a privileged control interface, how it differs from public explorer APIs, and what authentication does and does not protect.
Compact block filters: find relevant blocks privately
Learn how BIP 157 and BIP 158 help light clients find potentially relevant blocks, why matches can be false positives, and what validation still remains.
Block files, chainstate and undo data
Understand the different jobs of Bitcoin Core’s block files, UTXO database, undo records and indexes before planning storage or recovery.
AssumeUTXO: snapshots and background validation
Learn how Bitcoin Core boots from a recognized UTXO snapshot, what background validation still does, and why historical indexes can lag behind.