Nodes & software
A full node is what makes bitcoin's rules real. Every node independently verifies every block and every transaction against the consensus rules and rejects whatever fails, which is why nobody can spend coins they do not have even when a miner would happily help them.
Running one changes your relationship with the network. A wallet that queries somebody else's server trusts that server to tell the truth about your balance, and to not keep a log of which addresses you asked about. A wallet backed by your own node does neither. That is the practical reason nodes keep coming up in privacy discussions that look at first like they are about something else.
The section covers the software itself. Bitcoin Core is the dominant implementation and the de facto specification. Alternative implementations exist and matter, and the entries here are honest about the risk of running one. Pruning lets a node validate everything and then discard old blocks, which is what makes a full node practical on a laptop. Initial block download is the wait before any of it works.
RPC, the peer to peer message types that tie nodes to each other, and the sync strategies they use to catch up are here too, for the point where curiosity turns into a config file.
31 terms. Last reviewed 2026-09-07.
Terms in Nodes & software
- Addrv2Addrv2 is the peer-to-peer message bitcoin nodes use to gossip peer addresses the older addr message cannot express, each tagged with a one byte network id for Tor v3, I2P or Cjdns.
- AssumeutxoAssumeutxo lets a Bitcoin Core node start from a snapshot of the unspent output set at a hardcoded height, then verify the skipped history in the background.
- BIP-324 encrypted transportalso v2 transportBIP-324 encrypted transport is bitcoin's version 2 peer-to-peer link protocol, which encrypts every message exchanged between two nodes and makes the connection indistinguishable from random data to an eavesdropper.
- Bitcoin CoreBitcoin Core is the reference implementation of bitcoin, the descendant of Satoshi's original client and the software most of the network's validating nodes actually run.
- Bitcoin KnotsBitcoin Knots is an alternative bitcoin node implementation maintained by Luke Dashjr, consensus-compatible with Bitcoin Core but shipping stricter defaults for which transactions it will relay.
- Block explorerA block explorer is a website that lets you search the blockchain by transaction ID, address, or block, showing confirmations, fees, and amounts without running any software yourself.
- Blocks-first syncBlocks-first sync was bitcoin's original catch-up method, requesting blocks one at a time from a single peer and validating each before asking for the next.
- Bloom filteralso BIP37A bloom filter is a compact probabilistic set that BIP37 light wallets sent to a full node so the node would forward only transactions plausibly belonging to them.
- Compact block filterA compact block filter is a small Golomb-coded summary of the output scripts a block creates and spends, published by full nodes so a light wallet can test blocks without revealing what it owns.
- DNS seedA DNS seed is a domain name that answers with the IP addresses of reachable Bitcoin nodes, giving a freshly installed node somewhere to make its first connection.
- Electrum serveralso Electrum Personal ServerAn Electrum server indexes the blockchain by script and answers address queries for lightweight wallets, so those wallets get instant balances without downloading the chain themselves.
- Header chainalso Best header chainThe header chain is the sequence of 80 byte block headers a node has verified, which can run thousands of blocks ahead of the block data it has actually downloaded.
- Headers-first syncHeaders-first sync is the startup strategy where a node downloads and verifies the whole 80 byte header chain before requesting any block bodies, then fetches those bodies in parallel.
- Initial block downloadalso IBDInitial block download is the catch-up phase a new bitcoin node goes through, fetching and verifying every block from the genesis block to the current tip.
- Inventoryalso Inv messageAn inventory is the list of object identifiers a node advertises to its peers, saying what transactions and blocks it holds without sending any of them yet.
- Lightweight clientalso Thin client, SPV nodeA lightweight client is a wallet that holds no copy of the blockchain and asks other people's servers what happened to your addresses.
- MainnetMainnet is the live Bitcoin network, the one chain where coins have real value, running without interruption since the genesis block was mined on January 3, 2009.
- Message headerBitcoin's message header is a fixed 24 bytes of envelope wrapped around every peer-to-peer message: a network start string, a command name, a payload length, and a checksum.
- Neutrinoalso BIP157, Compact block filtersNeutrino is the light client design where your wallet downloads a tiny filter for each block, checks it locally, and only fetches the full blocks that might concern you.
- Nodealso Full node, Peer, Archival nodeA node is a computer running bitcoin software that stores the chain, checks every rule for itself, and relays valid blocks and transactions to its peers.
- P2P messagealso MessageP2P messages are the fixed vocabulary bitcoin nodes use to talk to each other: short commands like version, inv, getdata, tx, and block, sent over a plain TCP connection.
- Pruned nodeA pruned node validates the entire blockchain and then deletes the old block files it no longer needs, keeping full verification while giving up the archive.
- Regtestalso Regression test modeRegtest is a private Bitcoin network that runs on your own machine, where you mine blocks on command instead of waiting for anyone else to produce them.
- RPCalso JSON-RPC, Remote procedure callRPC is the command interface a bitcoin node exposes to other programs, letting a wallet, an exchange back end, or your own terminal ask it questions and issue instructions.
- Running a full nodealso Node runnerRunning a full node means keeping bitcoin software on a machine you control that downloads the chain, checks every rule itself, and answers your wallet's questions without asking anyone else.
- SignetSignet is a test network whose blocks are only valid if a designated signer has signed them, which keeps its ten minute block schedule steady instead of erratic.
- Simplified Payment Verificationalso SPVSimplified payment verification checks that a transaction sits in a block with real proof of work behind it, using only block headers and a merkle branch.
- Standard block relayStandard block relay is the original way a new block travels between nodes: announce the hash, wait for the peer to ask, then send the entire block over the wire.
- Start stringalso Network magicThe start string is the four-byte prefix at the front of every bitcoin network message, and it names which network the sender is on before anything else is read.
- Testnetalso Testnet4Testnet is a parallel Bitcoin network whose coins are deliberately worthless, used by wallet and exchange developers to rehearse transactions before touching anyone's real money.
- Unsolicited block pushAn unsolicited block push is a peer sending you a block you never asked for, skipping the usual announce-and-request handshake to save a round trip on time-critical data.
The other 13 sections
- BasicsWhat bitcoin is, what a satoshi is, and the handful of ideas the rest of the glossary is built on.
- Addresses & keysWhere coins get sent, what a private key actually controls, and how one seed produces thousands of addresses.
- Wallets & custodyHot, cold, custodial and multisig, and what each one changes about who can move your coins.
- Privacy & securityThe attacks that take people's bitcoin, and the habits and tools that stop them.
- Transactions & feesWhat a bitcoin transaction is made of, why it costs what it costs, and how to unstick one.
- Buying & exchangesOrder types, spreads and fee schedules: the vocabulary an exchange uses while it is charging you.
- Markets & investingMarket cap, volatility and spot ETFs. The language of price, without the price predictions.
- Mining & consensusHow new blocks get made, what difficulty adjusts, and why the rules hold with nobody in charge.
- Protocol & upgradesSegWit, Taproot, soft forks and BIPs: how bitcoin changes and who gets to decide.
- Lightning & layer 2Payment channels, invoices and routing, for moving bitcoin without paying for space in a block.
- Regulation & taxKYC, the Travel Rule, MiCA and capital gains: the rules that reach your account and your tax return.
- Culture & historyMt. Gox, the genesis block, HODL, and the events and slang that shaped how people talk about bitcoin.
- Developer referenceP2P message types, opcodes and script terms: the field names you meet reading bitcoin code.
Frequently asked questions
What does running a full node get me?
Your own copy of the rules. A node verifies every block and every transaction itself and rejects whatever fails, so your balance stops depending on somebody else's server being honest and online. It is also the strongest privacy available.
Do I need a node to use bitcoin?
No. Most people use lightweight wallets that ask a server about their addresses, which works and is what nearly every phone wallet does. A node matters when you want to stop trusting that server, or when you hold enough to care.
What does the initial sync involve?
Downloading and verifying the entire chain, which takes hours and a few hundred gigabytes on a first run. Pruned mode still checks every block and then discards the old ones, which keeps the disk requirement far smaller.
Is Bitcoin Core the only implementation?
It is the reference one and what most of the network runs, but not the only one. Alternatives such as Bitcoin Knots exist and follow the same consensus rules. Software diversity is healthy here; divergence in the consensus rules is not.