Introduction
Bitcoin mining supports the network by adding transactions to blocks, providing proof of work that makes confirmed history difficult to reverse, and issuing new bitcoin according to the protocol’s schedule. Block subsidies and transaction fees give miners an incentive to commit computing resources to this process.
Mining and validation work together. Miners and mining pools typically use full nodes to validate transactions and construct candidate blocks, while other full nodes independently check the blocks they receive. Hashing does not itself validate transactions, and producing proof of work cannot make an invalid block acceptable.
Together, these mechanisms allow participants to maintain an ordered transaction history without a central operator.
How a Miner Contributes a Block
A miner or mining pool constructs a candidate block using transactions available to its node, usually drawn from its mempool—the node’s collection of unconfirmed transactions. Transaction selection typically prioritizes fee rate while respecting transaction dependencies and other validity requirements.
The block includes a coinbase transaction through which the miner can claim the permitted reward. Its header contains a reference to the previous block, a Merkle root committing to the included transactions, and a nonce, among other fields.
Mining hardware repeatedly hashes the header, varying the nonce and updating other permitted data as needed. The goal is to find a header hash whose numerical value is less than or equal to the network’s proof-of-work target. There is no known practical shortcut to this search; miners perform repeated hash attempts until a qualifying result is found. See the Bitcoin block-header reference.
The miner then broadcasts the completed block. Each receiving full node checks the proof of work and the block’s other consensus requirements. For ordinary transactions, these checks include whether inputs spend available outputs and satisfy the relevant spending conditions.
Validation and chain selection are separate steps. A valid block may belong to a competing branch rather than immediately becoming part of a node’s active chain. Nodes select the valid chain with the greatest cumulative proof of work. An invalid block is rejected regardless of how much work was spent producing it.
Proof of Work and the Cost of Rewriting History
Each block header references the previous block’s header hash. Changing an earlier block therefore changes the references required by its descendants, so an alternative history needs new proof of work from the point where it diverges.
For example, an attacker might try to replace a confirmed payment with a conflicting transaction that spends the same funds back to themselves. To displace the accepted history, the attacker would need to produce a valid alternative chain with more cumulative work while honest miners continue extending their chain.
More confirmations increase the accumulated work an alternative history must overcome. This is why recipients often wait for multiple confirmations before treating a payment as settled. The appropriate number depends on the payment and the recipient’s risk assessment; no particular number makes reversal impossible.
Proof of work does not let an attacker bypass transaction rules. Replacement transactions and blocks must still be valid, and additional hashing cannot forge another user’s signature. The Bitcoin white paper explains this relationship between proof of work, confirmations, and double-spend resistance.
Mining Incentives: Block Subsidy and Transaction Fees
A block’s permitted reward consists of two components:
- Block subsidy: Newly issued bitcoin defined by the protocol’s issuance schedule.
- Transaction fees: The difference between the input and output values of the ordinary transactions included in the block.
Both components can be claimed through the block’s coinbase transaction. Together, they are commonly called the block reward.
The subsidy halves every 210,000 blocks, approximately every four years. It became 3.125 BTC per block at block height 840,000 in April 2024 and remains at that level until the next halving.
Transaction fees vary with demand for block space and the transactions included in a particular block. They are existing bitcoin transferred to miners, rather than newly issued bitcoin.
These rewards incentivize miners to commit hardware, electricity, and other resources to producing valid blocks. An invalid block cannot provide a spendable reward on the chain accepted by validating nodes. However, mining revenue does not guarantee profitability: a miner’s operating costs and other expenses still matter.
Difficulty Adjustment and Network Stability
Bitcoin targets an average block interval of 10 minutes. Individual blocks can arrive much sooner or later because discovery is probabilistic.
On Bitcoin’s main network, difficulty adjusts every 2,016 blocks—roughly every two weeks. The retarget calculation uses the elapsed time between the first and last block timestamps of the preceding difficulty period, subject to protocol limits.
If that measured time is shorter than the two-week target, difficulty increases and the numerical proof-of-work target decreases. A lower target means fewer possible hash outputs qualify, making block discovery harder. If the measured time is longer, difficulty decreases and the target increases.
Every full node can calculate the required target from the same chain data and consensus rules. The adjustment does not rely on an external hashrate estimate or manual intervention. The calculation is defined in Bitcoin Core’s proof-of-work implementation.
This mechanism helps block production stay near its intended long-term pace as miners join or leave the network. It does not guarantee a block every 10 minutes or eliminate short-term variations.
Mining Pools: Sharing Work and Reducing Payout Variance
A miner’s chance of finding the next block is approximately proportional to its share of total network hashrate—the rate at which miners perform hash attempts. For a small solo miner, the wait between successful blocks can be very long.
Mining pools combine contributions from many miners and use shares to account for their work. A share is a submitted proof of work that meets the pool’s assigned threshold. The pool normally sets a higher numerical target than the network target, so shares are easier to find than Bitcoin blocks.
Occasionally, a share also meets the network target. The pool can then broadcast the corresponding block. This process is described in the Bitcoin mining guide.
Pools distribute compensation according to their payout methods. Under Pay Per Share (PPS), eligible shares earn calculated payments regardless of whether the pool finds a block. Under Pay Per Last N Shares (PPLNS), payouts depend on pool-found blocks and the miner’s contribution over the relevant recent work window.
Pooling generally reduces individual payout variance compared with solo mining, although the degree of stability depends on the payout method. It does not change Bitcoin’s validation rules: every full node still independently checks blocks.
How ViaBTC’s PPS+ Method Fits In
ViaBTC’s PPS+ method applies PPS logic to the subsidy component and PPLNS logic to transaction fees.
The subsidy component is calculated from eligible contributed work at the applicable network difficulty, rather than depending on whether the pool finds a block. The transaction-fee component depends on fees from pool-found blocks and the miner’s contribution under ViaBTC’s PPLNS rules.
This means PPS+ does not make every part of a miner’s earnings fixed. Miners can consult ViaBTC’s official reward calculations for the current calculation, fees, and settlement terms.
Conclusion
Bitcoin mining helps participants agree on an ordered transaction history by producing blocks and committing proof of work. Accumulated work makes confirmed history harder to replace, while subsidies and transaction fees incentivize miners to continue contributing resources. Difficulty adjustment helps maintain the intended average pace of block production.
These functions operate alongside independent validation. Miners and pools typically use full nodes themselves, and other full nodes check that received blocks follow the rules. Nodes then select the valid chain with the greatest cumulative proof of work. Together, mining and validation support Bitcoin’s operation without a central authority.
FAQ
Does mining verify Bitcoin transactions?
Miners and pools typically use full nodes to validate transactions when preparing candidate blocks. The hashing process itself searches for qualifying proof of work; it does not check transaction validity. Other full nodes independently validate each block they receive.
How does Bitcoin mining help prevent double spending?
Mining establishes an ordering of transactions in a chain secured by accumulated proof of work. Full nodes reject transactions that spend outputs already spent in that chain. Replacing a confirmed payment with a conflicting valid transaction requires an alternative valid chain with more cumulative work.
Why does Bitcoin’s difficulty change?
Difficulty adjusts every 2,016 blocks to help keep the average block interval near 10 minutes as total network hashrate changes. The calculation uses recorded block timestamps, so it responds to observed block timing rather than directly measuring mining hardware.
What is the difference between the block subsidy and the block reward?
The subsidy is newly issued bitcoin defined by the protocol. It is 3.125 BTC per block during the halving period that began at block height 840,000. The block reward includes both the subsidy and transaction fees.
Does joining a mining pool change how Bitcoin validates blocks?
No. Pools coordinate mining work and distribute compensation according to their payout methods. Pool-found blocks must satisfy the same consensus rules as solo-mined blocks, and full nodes validate them independently.