Bitcoin mining is a lifecycle of separate roles: a wallet signs; nodes apply policy and relay; a template builder creates candidate work; a job distributor sends jobs; a hashing device searches; a publisher relays a candidate block; independent nodes validate; and nodes compare valid chains by accumulated work.
Lifecycle: Transaction to Most-Work Chain
Transactions, Policy, and Templates
A wallet creates and signs a transaction. Nodes independently apply consensus rules; they may also use local relay and mempool policy, which is not identical to consensus. A template builder selects candidate transactions and constructs a candidate block. BIP 22 and BIP 23 document a template interface; an ASIC does not automatically select transactions merely by receiving a job.
Header, Target, and Double-SHA256
The block header commits to the previous block, Merkle root, time, target encoding, and nonce. Mining repeatedly changes allowable header and template fields and evaluates double-SHA256. A result is eligible only when its hash is at or below the network target and the complete block passes validation.
Network Target Versus Pool Share Target
A pool can issue lower-difficulty share work for contribution accounting. A share target is not the network target, and an accepted share is not normally a Bitcoin block. Read the pool’s payout, custody, measurement, stale-work, and fee terms separately from protocol mechanics.
Who Does What?
| Role | Does | Does not establish |
|---|---|---|
| Wallet | Signs authorized spends | Block validity or mining payout |
| Node | Validates blocks and transactions | Every template or hash |
| Template builder | Constructs candidate work | Acceptance of invalid blocks |
| ASIC | Searches candidate headers | Independent transaction validation |
| Pool | May distribute work and administer payments | Protocol finality or universal template control |
Rewards, Variance, Difficulty, and Security Limits
A valid block’s coinbase may claim the subsidy permitted at that height plus included fees. Finding such a block is probabilistic. Difficulty adjustments follow consensus rules using prior block data; no current network snapshot is needed to explain the mechanism. More accumulated work makes a competing valid history harder to create, but does not prevent invalid blocks from being rejected, guarantee a reward, or create absolute finality.
Probability and Evidence Worksheet
- State the role you control: wallet, node, template, job distribution, hashing, or site operation.
- For payout analysis, record the pool method, fee, custody, accepted/stale definition, time window, and assumptions.
- For hashrate, separate local display, pool-effective rate, accepted shares, and inferred network estimates.
- For a security claim, state attacker share, confirmation depth, duration, propagation, and response assumptions.
Safe Next Steps
Read node and miner roles, hashrate measurement, pool payout accounting, site commissioning, and the mining operations risk register before making an operating decision.
Protocol Sources
Bitcoin whitepaper; revision-pinned Bitcoin Core proof-of-work code; revision-pinned BIP 22; and revision-pinned BIP 23.
Frequently Asked Questions
What does a Bitcoin miner actually do?
Mining hardware searches candidate block headers for a double-SHA256 hash below the network target. It does not by itself validate every transaction, choose every template, or make invalid blocks acceptable.
Who validates Bitcoin transactions and blocks?
Fully validating nodes apply their consensus rules to transactions and blocks. They reject invalid blocks even if a miner expended work on them.
What is a block template?
A template builder assembles candidate block data, including a transaction set and coinbase transaction, for hashing work. A pool or other job distributor may provide that template.
Is a pool share a Bitcoin block?
No. A pool can set an easier share target to measure submitted work. A share is accounting evidence under the pool arrangement; a Bitcoin block must meet the network target and pass node validation.
Does mining guarantee a reward?
No. Finding a qualifying hash is probabilistic. Pool arrangements can change the distribution of payments, but their terms, measurement, fees, custody, and operating risks remain relevant.
What may a valid block claim?
Its coinbase transaction may claim up to the subsidy permitted by the consensus rules at that height plus fees from included transactions. A template can claim less, and node validation still applies.
Does more hashrate make Bitcoin final?
More accumulated work can increase the work needed for a competing valid history, but confirmations reduce reorganization risk probabilistically rather than creating absolute finality.
Can a miner choose transactions?
It depends on the architecture. A pool or template service commonly controls the transaction set. Direct template control needs a validating node and compatible template and mining software.
