Proof of Work is the consensus mechanism Bitcoin uses to agree on which transactions are valid without a central authority. Competing to solve a computational puzzle, miners race to add the next block and earn newly created bitcoin. Deliberately, the puzzle is expensive to solve and trivial to verify. In mid-2026, Bitcoin's network was performing roughly 929 quintillion hashes per second, according to D-Central research.
The problem Proof of Work solves
Agreement among strangers who do not trust each other.
A payment network needs one shared record of who owns what. With a bank, the bank keeps it. Without one, thousands of independent computers need to converge on the same record, and someone has to decide which version is correct when they disagree.
With cost, Proof of Work answers that. Whoever has done the most computational work gets to write the next entry, and rewriting history would mean redoing all that work faster than the honest network adds to it. In the 2008 whitepaper, Satoshi Nakamoto described this as the core innovation.
How Bitcoin mining works step by step
Five steps, repeated roughly every ten minutes on Bitcoin.
- Miners gather pending transactions into a candidate block.
- Each miner combines the block with a changing number called a nonce and runs it through a hashing function.
- The output must fall below a target the network sets. No shortcut exists, so miners try billions of combinations per second.
- Whoever finds a valid hash broadcasts the block. Every other node verifies it in milliseconds.
- The winner receives the block reward, currently 3.125 BTC, plus the transaction fees inside the block.
That asymmetry between solving and checking is the whole design. Enormous effort to produce. Almost none to confirm.
Why the computational work secures Bitcoin
Security comes from the cost.
To rewrite a transaction, an attacker would need to redo the work for that block and every block after it, faster than the rest of the network extends the chain. With hashrate near 929 exahashes per second, that requires controlling more computing power than everyone else combined, which means acquiring hardware and electricity on a scale that costs more than any plausible attack could return.
The energy consumption is not a side effect. It is the mechanism.
Bitcoin's difficulty adjustment
Regardless of how many miners participate, Bitcoin targets one block every ten minutes.
Every 2,016 blocks, roughly two weeks, the protocol measures how fast those blocks arrived and adjusts the target. With more hashrate, the puzzle gets harder. With less, easier. In February 2026, difficulty reached 144.4 trillion after a 15% single-adjustment jump, then eased to around 124.9 trillion by mid-year.
Because of that feedback loop, Bitcoin's issuance schedule holds regardless of how much money floods into or out of mining.
Proof of Work vs Proof of Stake
| Proof of Work | Proof of Stake | |
|---|---|---|
| How blocks are added | Miners solve a computational puzzle | Validators selected by stake |
| Cost to participate | Hardware and electricity | Capital locked as collateral |
| Energy use | High by design | Minimal |
| Penalty for attacks | Wasted resources | Stake destroyed through slashing |
| Track record | Since 2009 without a successful rewrite | Ethereum since September 2022 |
| Used by | Bitcoin, Litecoin, Dogecoin, Monero | Ethereum, Solana, Cardano, Avalanche |
In 2022, Ethereum's switch cut its energy use by roughly 99.95%. Bitcoin has not followed and shows no sign of doing so, since its community treats the energy cost as a feature.
How much energy Bitcoin mining uses
Mining consumes real electricity. The Cambridge Centre for Alternative Finance reported a 52.4% sustainable energy mix in its 2025 study, comprising 42.6% renewables and 9.8% nuclear.
Two points get lost in most coverage. Tracking hashrate and reward value rather than transaction count, energy use makes "energy per transaction" a meaningless measure. And chasing the cheapest power available, miners frequently end up on stranded or surplus generation with no other buyer.
The mining pool centralization problem
Proof of Work has one weakness its defenders acknowledge: mining pools concentrate.
D-Central calculated the Nakamoto coefficient at 3 in mid-2026, meaning only three pools were needed to exceed half of all blocks produced. Foundry USA alone held roughly 27% of hashrate.
Pool concentration is not ownership concentration. At any time, individual miners can redirect their hashrate to a competitor. What pools control is transaction selection. In May 2026, seven of the largest pools, representing nearly 75% of hashrate, agreed to adopt Stratum V2, a protocol letting individual miners choose which transactions go into blocks.
Where mb.io fits
Proof of Work secures the asset. Acquiring it through a regulated venue is a separate question.
mb.io is a regulated crypto spot exchange backed by MultiBank Group, a financial institution founded in 2005 that serves more than 2 million clients across 100+ countries.
- Regulated by VARA in the UAE and AUSTRAC in Australia
- 10/10 security score from Hacken, an independent blockchain security auditor
- Institutional-grade MPC custody powered by Fireblocks, with segregated client funds
- A curated list of assets, so you're not sorting through thousands of tokens to find the ones worth trading
- Buy, sell, and swap in three steps, from sign-up to purchase
- 24/7 multilingual client support
Open your account and start trading on mb.io.
Frequently asked questions
What is Proof of Work in simple terms?
A way for a network to agree on valid transactions by having participants compete to solve a hard computational puzzle. Whoever solves it adds the next block and earns a reward.
Why does Proof of Work use so much energy?
By design. Because the computation costs so much, rewriting the blockchain is impractical. Remove the cost and the security goes with it.
Which cryptocurrencies use Proof of Work?
Bitcoin, Litecoin, Dogecoin, Monero, and Bitcoin Cash. Until September 2022, Ethereum used it, then switched to Proof of Stake.
How much does a Bitcoin miner earn?
The block reward of 3.125 BTC per block following the April 2024 halving, plus transaction fees. The reward halves again around April 2028.
What is mining difficulty?
The target a hash must fall below to be valid, adjusted every 2,016 blocks to keep block times near ten minutes. When hashrate increases it rises, and when hashrate drops it falls.
Has Bitcoin's Proof of Work ever been broken?
No. Since January 2009, the chain has run without a successful rewrite of confirmed transactions.
Is Proof of Work centralized?
Mining pools concentrate. Three pools produced over half of Bitcoin's blocks in mid-2026. Individual miners can switch pools at any time, and Stratum V2 adoption is shifting transaction selection back to them.
What is the difference between Proof of Work and mining?
Proof of Work is the consensus mechanism. Mining is the activity of participating in it. Miners run the hardware that performs the work.
