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What Is Crypto Mining?

What crypto miners actually do, why proof of work uses so much electricity, and how to spot fake mining offers and cryptojacking.

9 min read Free lesson Fact-checked Nov 2026

What is crypto mining?

Hi, I'm Block. Right now, buildings full of humming machines are making guesses as fast as electricity allows, all racing to win the same lottery, again and again, around the clock. That's crypto mining. In this lesson: what miners actually do, why it eats so much power, and the mining traps that cost ordinary people money.

Mining isn't digging

Last lesson, you saw two ways strangers agree on one version of the truth. Proof of work is the one that needs miners. And the name is misleading. Nobody is digging anything up. Miners are record keepers who have to prove they spent real effort before anyone accepts their page of the ledger.

Here's the job, step by step. People send transactions out to the network. A miner gathers a batch of them into a candidate block. Then the miner starts guessing, trying to find a winning number. When they find one, they broadcast the block to everyone, and if it checks out, they collect a reward.

So what's the guessing? Remember the digital fingerprint from the hashing lesson. The miner runs the block through that fingerprint function. Their goal is a fingerprint that starts with enough zeros to fall under a target number. If it misses, they change one small field, called the nonce, and try again.

There's no shortcut and no clever trick. Every guess is like scratching a lottery ticket. You can't study for it, and you can't get lucky on purpose. The only way to win more often is to scratch more tickets per second. That's why mining is a race of raw computing power, not brains.

More guesses per second, more chances to win.

Now, if more machines join, wouldn't blocks come faster and faster? Bitcoin aims for one block about every ten minutes. Every two thousand and sixteen blocks, roughly every two weeks, every node checks how fast blocks really came and adjusts the target.

Blocks coming too fast? The target gets harder to hit. Miners leaving and blocks slowing down? It gets easier. So adding machines doesn't print coins faster. It just makes each block harder to win.

More miners don't mean more coins. Just harder blocks.

Here's something people often get wrong, and it's worth clearing up. Miners choose which transactions go in a block and in what order. But every node checks every transaction in that block, and rejects the whole block if anything is invalid or already spent. A miner can't move your coins, because they don't have your key.

No key, no signature, no spending.

Why miners bother

So why would anyone spend a fortune on machines and electricity to do this? Because the winner of each block gets paid two ways. Brand-new coins created by that block, and the fees from every transaction inside it.

That fee part matters to you directly. Miners usually pick the transactions paying the highest fee for their size first. So when the network is busy, a low fee can leave your transaction waiting. That's not a bug, and it's not a sign of a problem with your wallet. It's an auction for space in the next block.

A stuck transaction usually means a low fee, not a hack.

The new-coin part is on a fixed schedule. When Bitcoin started, each block created fifty new coins. Every two hundred and ten thousand blocks, about every four years, that number is cut in half. That's the halving. Fifty, then twenty-five, then twelve and a half, and so on.

New coins per block halve about every four years.

Keep halving forever and the total never passes twenty-one million coins. Around the year twenty-one forty, new coins stop entirely. After that, miners are paid only by fees. Nobody can quietly create more, because every node would reject the block.

Extra coins? Every node would reject the block.

In the early days, people mined on ordinary home computers. As more people joined and difficulty climbed, that stopped paying. Mining moved to machines called ASICs. That's short for application-specific integrated circuit: a chip built to do exactly one thing, run that fingerprint function, over and over.

And because one machine alone might go a very long time without winning a block, most miners join a pool. Think of an office lottery syndicate. Members combine their guessing power, the pool wins blocks more often, and the reward is split by how much work each member contributed. Smaller, steadier payouts instead of a rare jackpot.

Pools trade jackpots for steady pay.

Why so much power?

Now the big question: why does all this use so much power? Here's the part that surprises people. The cost isn't a side effect. It's the security system.

Remember from the blocks and chains lesson: each block is locked to the one before it. To rewrite history, an attacker would have to redo the work for that block and every block after it, and then outrun everyone else who's still mining. Every guess costs electricity, so cheating costs a fortune.

Rewriting history means outspending everyone.

And the bill is real. A study from the University of Cambridge estimated that Bitcoin mining uses roughly half a percent of all the electricity used in the world. That's a lot of power for one network.

Where that power comes from is part of the debate. The same study found just over half came from sustainable sources: mostly renewables like hydro and wind, plus some nuclear. The rest was mainly fossil fuels. People disagree strongly about whether that trade is worth it. But now you know what the trade actually is, and you can judge it for yourself.

Security paid for in electricity.

Proof of stake, the other method from last lesson, avoids that bill. Ethereum used mining until it switched to proof of stake, and its own estimate is that the switch cut its energy use by about ninety-nine point nine five percent. Instead of burning electricity, validators put coins up as a deposit they can lose.

Work burns electricity. Stake risks coins.

Here's what happens when a mined network doesn't have enough honest power behind it. Ethereum Classic, a smaller proof of work coin, was hit by repeated attacks in which someone controlled most of the mining power. In one, they rewrote thousands of blocks and spent the same coins twice.

In the first attack alone, more than eight hundred thousand coins were spent twice. That's why exchanges make you wait for several confirmations before a deposit counts. Each new block on top makes a rewrite harder. It's not red tape. It's protection against exactly this.

Confirmations are a safety wait.

Mining traps

Now the part I care about most: where mining turns into a way to lose money. There are two big ones. Mining offers that sell you a share of machines you'll never see. And mining that happens on your own devices without your permission.

The pitch usually arrives out of the blue, and it sounds like this. You don't need machines or cheap electricity. Just rent a share of ours, and watch the earnings roll in every day. Then come the guaranteed returns, the bonus for recruiting friends, and a timer.

This isn't hypothetical. One cloud mining service sold more than five hundred and fifty million dollars in mining contracts. U.S. prosecutors say it had less than one percent of the computing power it claimed, and paid early withdrawals with crypto it simply bought. The dashboard showed earnings. The machines mostly didn't exist.

A dashboard isn't proof of a machine.

So here's how to read any mining offer. Real mining profits rise and fall with difficulty, fees and power costs, so nobody honest can promise a fixed daily return. If it's guaranteed, if it pays you to recruit, or if you have to pay to withdraw, walk away.

Guaranteed mining returns? Walk away.

The second trap is quieter. It's called cryptojacking. Criminals sneak mining software onto your computer or phone, usually through a bad link, a booby-trapped website, or a fake free app. Then your device mines for them in the background, on your electricity.

Watch for the signs. A device that suddenly runs slow. A fan that won't quiet down or a battery that runs hot. Apps crashing or the device shutting itself off. And an electricity bill that jumps for no reason. A hot, slow device can be a symptom, not just old age.

Hot and slow for no reason? Check it.

The defense is basic hygiene. Keep your system and browser updated. Don't install apps or browser extensions that promise free crypto for mining on your phone. Use a reputable ad and script blocker. And if a device is acting strangely, don't use it for your crypto until it's been checked or reset.

Acting strange? Keep it away from your crypto.

Mining in four lines

Here's the whole lesson in four lines. Miners bundle transactions and win the right to add a block by guessing. Difficulty keeps blocks steady, and halvings shrink new coins over time. The electricity is what makes rewriting history so expensive. And any mining offer with guaranteed returns is a trap.

Mining secures the chain. It doesn't guarantee anyone a profit.

Sources

Education only. Not financial advice.

Education only. Not financial, investment, tax or legal advice. Block, our on-screen presenter, is AI-generated, voice included; the research and scripts are ours.