Crypto mining is the process in which computers compete to add the next block of transactions to a proof-of-work blockchain, and the winner earns newly created coins plus transaction fees. It is how Bitcoin and some other networks stay secure without a central authority.
Mining is often misunderstood as “computers solving complicated maths for free money”. The reality is more specific, and far less casual: it is an industrial activity with real costs, real competition and real risks. This guide explains how mining works, what miners earn, why the energy use is intentional, and what a beginner should know. For context, see what is blockchain and what is Bitcoin.
Key takeaways
- Miners gather pending transactions into a block and race to find a valid hash; the winner adds the block and is paid.
- The “work” is deliberately costly, which makes rewriting history very expensive for attackers.
- Rewards come from a block subsidy that shrinks over time, plus fees.
- Mining at home is rarely profitable on major networks because of specialised hardware and electricity costs.
How mining works step by step
A proof-of-work network needs a way for strangers to agree on which transactions happened and in what order. Mining solves this. Here is the process on a network like Bitcoin:
- Users broadcast transactions, which wait in the mempool (see how crypto transactions work).
- A miner selects transactions, checks they are valid and assembles a candidate block, including a special transaction that pays the miner.
- The miner repeatedly runs the block’s data through a cryptographic hash function, changing a number called a nonce each time, looking for a result below a target value.
- There is no shortcut. The only way to find a valid result is trial and error, at enormous scale.
- The first miner to find one broadcasts the block. Other nodes quickly verify it, which is easy, and add it to their copy of the chain.
- The miner receives the block reward, and everyone starts work on the next block.
The target value adjusts automatically so that, on Bitcoin, a block is found about every ten minutes on average, no matter how many miners join or leave. This is called difficulty adjustment. More miners means a harder puzzle, not faster blocks.
What miners earn
Miners are paid in two ways. The first is the block subsidy: newly created coins awarded per block. On Bitcoin this subsidy is cut in half roughly every four years in an event described in Bitcoin halving explained. The second is transaction fees paid by users. Over time, fees are expected to make up a larger share of income as the subsidy falls.
Mining is a business of margins. Income depends on the coin price, the miner’s share of total network computing power, and the number of blocks found. Costs include hardware, electricity, cooling, hosting and maintenance. If the price falls or difficulty rises, less efficient miners can turn unprofitable and switch off.
Illustrative example
These round numbers are invented for explanation. Imagine a miner controls 1 percent of a network’s total power. Over a long period, that miner would expect to find about 1 percent of the blocks. If 100 blocks are found in a day, the expected result is one block, though luck varies a lot in the short term. If the value of that block and its fees is less than the electricity and equipment costs for the day, the miner loses money.
Types of mining hardware and pools
| Hardware | Used for | Notes |
|---|---|---|
| CPU / ordinary computer | Early Bitcoin days; a few small coins | Now far too slow for major networks |
| GPU (graphics card) | Some proof-of-work coins | Flexible, but less efficient than specialised chips on big networks |
| ASIC (specialised chip) | Bitcoin and other major hash-based coins | Very efficient, expensive, loud and hot, and useful for one algorithm only |
Because finding a block is a lottery, individuals usually join a mining pool. The pool combines the power of many members, and rewards are shared in proportion to contributed work, minus a fee. This gives smaller miners smoother, more predictable income.
Why does mining use so much energy?
The energy use is not a bug; it is the security model. Because producing a valid block requires real-world resources, an attacker who wanted to rewrite history would need to out-spend the entire honest network on hardware and power. The more competition there is, the more expensive an attack becomes.
Critics point to the large electricity consumption and associated emissions, depending on the power source. Supporters note that miners seek cheap energy, can use surplus or otherwise wasted power and can add flexible demand to grids. Both views contain real arguments, and the facts vary by region and over time, so be careful with headline numbers. Proof-of-stake is an alternative that secures a network with locked-up capital rather than electricity; compare them in proof of work vs proof of stake.
Security: what is a 51 percent attack?
If a single party controlled more than half of a proof-of-work network’s total computing power, it could in theory reorder recent transactions and spend the same coins twice. This is called a 51 percent attack. On large networks such as Bitcoin, acquiring that much power would be extremely expensive and would likely damage the value of the attacker’s own investment. Smaller proof-of-work coins, which have less total power behind them, have suffered such attacks in the past. This is one reason the size of a network matters when judging its security.
Should a beginner try mining?
This is an educational overview, not advice. Realistically, mining the largest coins at home on a laptop or a phone is not viable. Beware of the following:
- Cloud mining contracts that promise guaranteed daily returns. Many have been scams, and guaranteed returns are a classic red flag; see crypto scams.
- Free mining apps that request wallet access or payment.
- Hidden malware (cryptojacking) that uses your device to mine for someone else.
- Hardware risk: machines lose value quickly as newer, more efficient models appear, and rules or taxes on mining income may apply where you live.
If you are curious, you can learn a great deal by reading about difficulty, hash rate and block explorers without buying any equipment. Many beginners find that simply holding or using a coin teaches them more than mining does. Our glossary at crypto glossary explains terms such as hash rate and nonce.
Is crypto mining legal?
In many countries it is legal, but some restrict or ban it, and energy rules or taxes may apply. Check the laws where you live before investing in equipment.
Can I mine Bitcoin on my phone or laptop?
Not in any meaningful way. The network is dominated by specialised machines, so a phone or laptop would almost never earn a reward and could be damaged by heavy use.
What is hash rate?
Hash rate is the total number of hash calculations per second performed by a miner or by the whole network. A higher network hash rate generally means stronger security.
Does Ethereum still use mining?
No. Ethereum moved from proof-of-work to proof-of-stake in 2022, so it no longer has miners. It now relies on validators.
What happens when all coins are mined?
For Bitcoin, the block subsidy will keep shrinking until around the year 2140. Miners are then expected to be paid by transaction fees alone, though how well that works in practice remains an open question.
Next step: compare the two main security models in proof of work vs proof of stake and see how supply is scheduled in Bitcoin halving explained.
