Mining & consensus
Mining is often described as solving complex maths problems. It is not. Miners guess numbers, hash the block header with each guess, and keep going until a hash lands below the target. The work is deliberately dumb and deliberately expensive, and that expense is the security.
Difficulty is the self correcting part. Every 2,016 blocks the network retargets so blocks keep arriving roughly every ten minutes, however much hashrate has joined or left. Nobody adjusts it and nobody can override it. The block subsidy halves every 210,000 blocks, and that schedule is what enforces the supply cap.
Consensus is the other half of the section, and it is where the terms get slippery. A block that gets orphaned is not the same as one that goes stale. A chain reorganisation is routine at one block and alarming at six. Selfish mining sits here too, along with the distinction between consensus and consensus rules that most explanations skip. The fork vocabulary lives under protocol and upgrades, and the 51 percent attack under privacy and security, because both are about what someone does to the network rather than how it runs.
Pools, ASICs, hashrate and the energy question are here too, because an honest answer about how much electricity bitcoin uses starts with knowing what a terahash is and who is paying for it.
37 terms. Last reviewed 2026-09-24.
Terms in Mining & consensus
- ASICalso Application-specific integrated circuit, Mining rigAn ASIC is a chip built to do one job, and in bitcoin that job is guessing SHA-256 hashes, which it does thousands of times faster per watt than any general purpose computer.
- Bitcoin miningalso Mining, MinerBitcoin mining is the competition to add the next block of transactions to the blockchain, in which specialized machines guess trillions of hashes for a reward paid in new coins and fees.
- BlockA block is one batch of bitcoin transactions plus the 80 byte header that seals it, added to the chain roughly every ten minutes by whichever miner solves it first.
- Block headeralso HeaderA block header is the 80 byte summary of a block: version, previous header hash, merkle root, timestamp, nBits, and nonce, and it is the part miners actually hash.
- Block heightalso HeightBlock height is the number of blocks in the chain before a given block, which makes the genesis block height 0 and the block mined after it height 1.
- Block rewardThe block reward is everything a miner is paid for a block: the newly issued subsidy plus every transaction fee inside it, claimed in the block's first transaction.
- Block sigop limitThe block sigop limit caps every bitcoin block at 80,000 units of signature operation cost, a verification budget counted separately from the 4,000,000 weight unit size budget.
- Block subsidyThe block subsidy is the brand new bitcoin created in each block, fixed by code at 50 coins in 2009 and halving every 210,000 blocks until it reaches zero.
- Block weightBlock weight measures a bitcoin block on a scale where a byte of witness data costs 1 unit and every other byte costs 4, capped at 4,000,000 units.
- Chain reorganizationalso Reorg, Blockchain reorganizationA chain reorganization is what happens when your node discovers a branch with more accumulated work, disconnects the blocks it had accepted, and rebuilds the tip along the new branch.
- Coinbase maturityalso Coinbase maturity ruleCoinbase maturity is the consensus rule that locks a block's newly created coins for 100 further blocks before any transaction is allowed to spend them.
- ConsensusConsensus in bitcoin is the state where independently run nodes, following identical rules, agree on one chain: the valid chain carrying the most accumulated proof of work.
- Consensus rulesConsensus rules are the validity checks every full node applies to a block, and breaking even one of them makes that block invalid no matter how much work it carries.
- Difficulty adjustmentalso RetargetThe difficulty adjustment is the rule that resets how hard mining is every 2,016 blocks, pulling the average time between blocks back toward ten minutes as hash rate changes.
- Genesis blockalso Block 0The genesis block is the first block of the bitcoin chain, hard coded into the software on January 3, 2009, and the only block whose 50 coin reward can never be spent.
- Halvingalso Halvening, Bitcoin halvingThe halving is the moment, every 210,000 blocks, when the new bitcoin paid to miners is cut in half, tightening bitcoin's issuance on a schedule nobody can change.
- Hash ratealso Hashrate, Hashing powerHash rate is the number of hash attempts the mining network makes each second, the standard measure of how much computing work is defending bitcoin at any moment.
- HashpriceHashprice is the daily revenue a miner earns per unit of computing power, usually quoted in dollars per petahash per day, and it is the number that decides whether a machine is worth running.
- Maximum block sizealso Block size limitMaximum block size is the ceiling on how much data one bitcoin block may carry, and since SegWit that ceiling is a four million weight unit budget rather than a byte count.
- Merkle blockalso Partial merkle branchA merkle block is the reply a light wallet gets when it asks for filtered block contents: the 80 byte header plus just enough hashes to prove which transactions matched.
- Merkle rootThe merkle root is the single 32 byte hash in a block header that commits to every transaction in that block, in the exact order the miner arranged them.
- Merkle treeA merkle tree is the hash pyramid that compresses every transaction in a block down to a single 32 byte value, so any one payment can be proved without the rest.
- Mining difficultyalso Difficulty, Network difficultyMining difficulty is the dial the network turns every 2,016 blocks to keep blocks arriving about ten minutes apart, no matter how much or how little hash rate shows up.
- Mining poolA mining pool combines the hash rate of thousands of separate miners so they share block rewards in small, regular payments instead of each waiting years for a block of their own.
- nBitsalso Compact targetnBits is the four byte field in every block header that packs the mining target into a compact, floating point style encoding of one exponent and a three byte coefficient.
- NonceA nonce is the four byte counter in a block header that miners increment while searching for a hash below the target, giving only 4,294,967,296 tries per header.
- Orphan blockAn orphan block is a block whose parent your node has not seen yet, so it cannot be validated or connected, which is not what most people mean when they say the word.
- Previous block header hashThe previous block header hash is the 32 byte field in every block header that names its parent, and it is the single link that turns a pile of blocks into a chain.
- Proof of workalso PoWProof of work is the rule that a block only counts once its header hashes below a target, so publishing a valid block costs real electricity that anyone can verify in milliseconds.
- Selfish miningSelfish mining is a strategy where a miner hides a solved block and releases it only to invalidate a rival's, earning more than its share of hash power should pay.
- Serialized blockA serialized block is the exact byte string a block becomes on the wire or on disk: the 80 byte header, a transaction count, then every transaction in order.
- SHA-256also SHA256SHA-256 takes an input of any length and returns a 32 byte fingerprint that is identical every time, unpredictable in advance, and impossible to work backwards from.
- Solo miningSolo mining means pointing your machines at your own node and keeping the entire block reward when you win, accepting that you may never win at all.
- Stale blockA stale block is a fully valid block that lost the race: another block of the same height won, so the network built on that one and abandoned this one.
- Stratum V2also SV2Stratum V2 is the rewritten protocol between miners and pools that encrypts the connection and lets the miner, rather than the pool, choose which transactions go into the block.
- Target thresholdalso TargetThe target threshold is the 256 bit number a block header hash must fall at or below for the block to count as valid proof of work.
- Version 2 blockalso V2 blockA version 2 block is a block whose header version field is 2, the upgrade that made BIP34 require the block's own height as the first item in its coinbase script.
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.
- 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.
- Nodes & softwareBitcoin Core, full nodes, pruning and RPC: the software that enforces the rules.
- Developer referenceP2P message types, opcodes and script terms: the field names you meet reading bitcoin code.
Frequently asked questions
Do miners solve complex maths problems?
No, and the phrase misleads. They guess numbers, hash the block header with each guess, and repeat until a hash lands below the target. The work is deliberately dumb and deliberately expensive, and that expense is what secures the chain.
Can I still mine bitcoin profitably at home?
Almost certainly not on residential electricity. A current machine draws more power than a standard household circuit supplies, makes roughly as much noise as a vacuum cleaner, and loses money above about five cents per kilowatt hour.
What is the difficulty adjustment for?
Keeping blocks arriving roughly every ten minutes however much hardware is running. Every 2,016 blocks the network retunes the target, so more miners joining makes mining harder rather than making coins appear faster.
What happens to miners when the subsidy runs out?
Transaction fees have to replace it. The subsidy halves every 210,000 blocks and reaches zero around 2140, and whether fees alone can pay for the same security is the longest-running open question in bitcoin.