Mining & crypto FAQ

Proof-of-work is a way to make it expensive to propose the next block. A miner repeatedly hashes a block header, changing one field each time, until the digest happens to fall below a target number. There is no shortcut: the only way to find a valid digest is to keep guessing. Once found, anyone can verify it with a single hash, so the work is cheap to check and costly to produce — which is what makes the chain expensive to rewrite.

See also: Why does mining need to burn energy at all?

#what-is-proof-of-work

A hash function takes any input and returns a fixed-length string of characters, called a digest. The same input always produces the same digest, but you cannot work backwards from a digest to the input, and changing one character of the input produces a completely different digest. Bitcoin uses SHA-256, which always returns 256 bits — 64 hexadecimal characters — no matter how large the input is.

See also: What is SHA-256, and why does the algorithm matter?

#what-is-a-hash-function

Hash rate is the number of hash guesses a machine or a network performs per second — kH/s, MH/s, GH/s, TH/s, PH/s, EH/s, each a factor of a thousand. A miner is rated in TH/s; a large network is measured in exahashes per second. Your share of the network, and therefore your share of the rewards, is your rig’s hash rate divided by the network total.

See also: What determines how much a rig earns?

#what-is-hash-rate

Difficulty is a number that sets how hard it is to find a valid block, by scaling the target a block hash must fall below. Bitcoin retargets every 2,016 blocks — about two weeks — aiming for one block every ten minutes. If blocks came too fast because hash rate rose, difficulty goes up; if miners switch off and blocks slow down, it goes down. This is the number your revenue is divided by, and it is the reason old hardware eventually stops paying.

#what-is-difficulty

An append-only list of blocks in which each block contains the hash of the block before it. Changing any block changes its hash, so altering an old block would break every link after it and be obvious to every node. Nodes independently follow the chain with the most accumulated proof-of-work, so agreement comes from the most expensive valid history rather than from a vote or a central authority.

#what-is-a-blockchain

No — it is pseudonymous and permanently public. Every transaction is recorded forever and anyone can read the ledger, but addresses are not names. The link is made at the edges: an exchange that verified your identity and knows your withdrawal address, or a pool that pays out to an address tied to your account. That matters for miners specifically, because a pool payout address is a public, long-lived link between your identity and your income.

#is-crypto-anonymous

Almost certainly not, unless your electricity is close to free. An S9 runs about 97 joules per terahash, which is roughly three times worse than an S19 and nearly six times worse than an S21. At a typical domestic rate it loses money every hour it runs, and the loss grows as difficulty rises. The honest test is the break-even number: if your all-in power price is above the rig’s break-even rate on the calculator, it is finished — unless you have a specific use for the heat.

See also: How do I work out my break-even electricity price?

#is-my-s9-still-profitable

Divide expected daily revenue by the kilowatt-hours the rig burns in a day. Revenue comes from your share of network hash rate times the daily block reward times the coin price; consumption is watts times 24, divided by 1,000. The result is the price per kilowatt-hour at which the machine exactly breaks even. Below it you earn something; above it you are paying to heat your garage. The calculator on the home page does this for every common rig at your own price.

See also: What is the difference between efficiency and hash rate?

#how-do-i-work-out-break-even-electricity-price

Hash rate is how much work a machine does; efficiency — joules per terahash, J/TH — is how much electricity it spends doing it. Hash rate decides how much of the reward you get, but efficiency decides whether getting it is worth anything, because power is the dominant ongoing cost. When comparing two rigs, compare J/TH first: a machine with half the hash rate and half the J/TH will often earn more net than the bigger one.

See also: Does underclocking improve efficiency?

#efficiency-vs-hash-rate

Usually, yes — and it is the single most useful trick for old hardware. Power draw does not scale linearly with clock speed: the chips need disproportionately more voltage to run faster, so dropping the frequency a little cuts power a lot. You lose some hash rate and save more electricity, which improves J/TH even though the machine is slower. The trade-off has a limit, and below a certain point the fixed overhead of the control board and fans starts to dominate, so efficiency gets worse again.

See also: What does firmware like Braiins OS+ or VNish actually change?

#does-underclocking-improve-efficiency

Stock Bitmain firmware gives you almost no control: a fixed frequency, a fixed fan curve, and a preset list of pools. Alternative firmware adds frequency and voltage tuning, autotuning per hash board, custom fan curves for noise or heat, and unrestricted pool configuration. On old hardware that is the difference between a machine that cannot pay for itself and one that can. Flashing is not risk-free — a failed flash can brick a control board, and it voids any remaining warranty — so read the recovery procedure first and expect to need it once.

#what-does-mining-firmware-change

Insist on a screenshot of each hash board reporting individually — a rig with one dead board still boots and still looks fine in a listing photo. Ask for the running power draw at the wall, not the nominal spec, because that is where a tired unit shows itself. Check the model number on the control board against the advertised model, since older Bitmain chassis are routinely re-labelled with newer model names. Confirm the PSU is included and matches your mains voltage, and prefer a seller who will show a live video of it hashing. A price that is far below everyone else is information, not an opportunity.

See also: Is it worth buying a whole secondhand rig or building from parts?

#buying-used-asic-what-to-check

A complete tested rig is the better first purchase: you get a working machine, a known PSU and a known firmware state, and you learn what normal looks like before you start troubleshooting. Parts are cheaper per board but you are buying someone else’s diagnosis, and a hash board that fails on arrival is your problem, not theirs. Once you already have a running machine and can tell a bad board from a bad PSU, buying spares to keep it alive is sensible — especially for a model you own several of.

#secondhand-rig-or-parts

It varies too much for this site to quote a figure. Prices move week to week with the coin price, differ by an order of magnitude between a tested unit with a PSU and an untested bare board, and depend on shipping and whether the seller will warranty it. We deliberately store no price for most models rather than publish a number that would be wrong within a month. Look up the current market yourself, then put your own figure into the payback calculation.

See also: Is it worth buying an old rig at all, or should I buy something newer?

#what-does-a-used-asic-cost

It depends on what you already own and what you pay for power. If you have free or stranded electricity, an old machine is nearly pure profit because its cost is already sunk — the secondhand price of an S9 reflects that it only works in that situation. If you are paying market rates, efficiency is everything and a newer machine wins, but the purchase price is the catch: an efficient rig costs real money and takes a long time to repay, and the arithmetic changes entirely if the coin price falls. Buy hardware you can afford to write off.

See also: Why do old rigs get switched off first?

#old-rig-or-new-rig

Because they have the worst ratio of revenue to power cost, and that ratio is what mining pays for. Network difficulty rises over time and the block subsidy halves on a fixed schedule, so the revenue per terahash ratchets down while an old machine’s joules per terahash stay where they were. The result is a moving line: as difficulty climbs, the break-even electricity price falls, and the least efficient machines on the network are the first to cross it. Every retarget pushes a few more of them over the edge.

#why-do-old-rigs-get-switched-off-first

One small rig, maybe; a serious machine, not without electrical work. A 1,300 W S9 draws roughly 11 A at 120 V, which is most of a 15 A circuit — and a circuit should not run continuously above 80% of its rating. The larger machines draw 3,000 W or more and need a dedicated 240 V circuit, which is why most home miners pay an electrician before they pay for the second rig. Check the rating on the breaker and the gauge of the wire rather than the socket in the wall.

#power-circuit-for-a-miner

Loud enough that you will not want to share a room with it. Small 90 mm fans on the older rigs run at several thousand RPM and produce something in the region of a vacuum cleaner at close range. That is why home miners put them in garages, basements or outbuildings, and why immersion and custom cooling are popular: quieting a machine usually means slowing or replacing its fans, which raises chip temperatures unless you change the cooling medium too.

#how-loud-is-a-miner

Yes, and for an old rig on cheap power it is often what makes the whole thing worthwhile. A machine is a resistive heater that pays you: almost all the electricity it consumes comes out as heat, and the hashing is effectively free once you were going to heat that space anyway. Air-cooled rigs ducted into a garage, greenhouse or workshop in winter are the common version; hydronic loops are the tidier one. In summer the heat is a liability, because you have to move it outside or pay to air-condition it away.

See also: Is my Antminer S9 still profitable?

#can-i-use-miner-heat

Only if you understand that you are buying a lottery ticket. Solo, your expected income is the same as in a pool — your share of the network times the block reward — but the variance is not: you are paid nothing at all until you find a full block. On Bitcoin, one old rig’s expected wait for a block is measured in centuries, so the realistic expectation is zero. Solo makes sense with a very large share of hash rate or on a chain with low total difficulty, where blocks actually arrive.

See also: What do PPS, FPPS and PPLNS mean?

#solo-mining-vs-pool

Longer than the model stays profitable, is the useful framing. The chips themselves usually outlive their usefulness by years, but the mechanical parts age: fans are the first failure, then the PSU, and thermal paste and pad degradation gradually raises temperatures, which in turn raises the fan speed and lowers the hash rate. The 17-series has a specific reputation for hash board failures under heat. Keeping intake air cool and filters clean is the cheapest lifetime you can buy, and spare fans are worth having on the shelf.

#how-long-does-a-miner-last

Not in the way a PC can, and that is why crypto-mining malware targets GPU machines and desktops rather than ASICs. An ASIC runs one algorithm in dedicated silicon with minimal firmware, and everything it produces goes to the pool account and payout address you configured — so there is nothing to steal except the machine itself. The real risks are mundane: leaving the web interface on a default password and reachable from the internet, and buying a secondhand unit that still has someone else’s pool credentials configured. Change the password and wipe the pool settings before you plug it in.

#is-mining-malware-a-problem

Not competitively. A GPU is a general-purpose processor that mines many algorithms reasonably well and holds resale value because it does other work. An ASIC is silicon designed for exactly one algorithm — orders of magnitude more efficient at that one thing, and useless for anything else. On any chain with a large SHA-256 ASIC ecosystem, GPU mining is not a slower route to the same result; it is a route that loses money on every hash. If you already own a GPU, point it at a memory-hard algorithm instead.

See also: What is the difference between efficiency and hash rate?

#asic-vs-gpu-mining

It is worth doing the arithmetic, because an ASIC is tied to an algorithm rather than to a coin — any SHA-256 chain will run on the same machine. A smaller chain usually has far lower total difficulty, so a single rig takes a much larger share of its rewards, which can more than offset a lower coin price. The catch is that a smaller chain also means less liquidity, a thinner market for what you mine, and much more price risk. Check the difficulty, the block reward and the actual market for the coin before moving a machine over.

#should-i-mine-altcoins-on-old-hardware

Four things: your hash rate, the network’s total hash rate, the block reward, and the coin price. Your share of the network is your hash rate divided by the network total, and it sets how much of the daily reward pool you receive. Nothing you do changes the other three. That is why a miner’s income falls whenever new hardware joins the network, even though the machine in front of them has not changed at all.

See also: What is difficulty?

#what-determines-how-much-a-rig-earns

The block reward has two parts: the subsidy, which is new coins issued on a fixed schedule, and the fees paid by the transactions the miner included. Bitcoin began at 50 BTC per block in 2009 and halves every 210,000 blocks. After the April 2024 halving it is 3.125 BTC, and the next halving is expected around 2028. Fees are typically a few percent on Bitcoin and vary with congestion, which is why a fee-heavy day shows up as a slightly better payout.

See also: What is a halving?

#what-is-the-block-reward

A halving cuts the block subsidy in half, on a schedule written into the protocol rather than decided by anyone. Bitcoin halves every 210,000 blocks — roughly every four years, with the next expected around 2028. If the coin price does not move, your revenue per terahash halves the day it happens. Operators respond by switching off their least efficient machines, which drops network difficulty and partly offsets the cut for whoever keeps running.

See also: Why do old rigs get switched off first?

#what-is-a-halving

A pool lets many miners combine hash rate and share the reward, so income arrives steadily instead of in lottery-sized lumps. You submit shares — hashes meeting an easier target than a real block — as proof of work, and the pool pays out by its scheme. Choose on payout scheme, fee (usually 0 to 3%) and server location, because latency to the pool costs you stale shares. A pool that is closer and charges slightly more is often the better deal.

See also: What do PPS, FPPS and PPLNS mean?

#what-is-a-mining-pool

They are pool payout schemes. PPS pays a fixed amount per share, so the pool carries the luck and charges a higher fee for it. FPPS does the same but includes expected transaction fees. PPLNS pays out only from blocks the pool actually finds, shared among recent contributors, so your income is lumpier and you carry more variance in exchange for a lower fee. For a single machine, the difference matters less than the pool’s uptime and how far away its servers are.

#pps-vs-pplns

A fee is what someone attaches to a transaction to make it worth including. Block space is capped, so when more transactions are waiting than fit in a block, miners include the highest-paying ones first and a fee becomes a bid rather than a price. You receive those fees only when your pool finds a block, and the pool distributes them by its own scheme — under PPS you get none of the upside, under FPPS or PPLNS you get some.

See also: What is the block reward?

#what-are-transaction-fees

Miners would be paid from fees alone. Bitcoin’s last subsidy is expected around 2140, and the fee share has been creeping up for years. Whether fee revenue can sustain a hash rate expensive enough to be worth attacking is a genuine, unresolved economic question about the long-run design — not a settled detail, and not something to plan a rig purchase around. The nearer-term version of the same pressure is the next halving.

#what-happens-when-subsidy-runs-out

It is arithmetic, not a yes or no, and the arithmetic is unforgiving. Revenue per hash is the daily block reward times the coin price divided by network hash rate. Cost per hash is your machine’s joules per terahash times your electricity price, plus pool fees, cooling and downtime. Both sides move constantly while the hardware cost is already sunk, and network difficulty only ratchets one way over any horizon that matters. Nothing here is investment advice.

See also: How do I work out my break-even electricity price?

#is-mining-profitable

Ten minutes was a design choice by Satoshi Nakamoto, balancing faster settlement against how often two miners find a valid block at nearly the same moment and force the network to choose between them. Block time is a target, not a guarantee: difficulty only retargets every 2,016 blocks, so a sudden hash-rate change makes blocks come faster or slower until the next adjustment. Because the search is random, gaps of an hour happen on a perfectly healthy chain.

#why-ten-minute-blocks

The first confirmation takes one block on average — about ten minutes for Bitcoin — but that is a mean, not a schedule, and the wait depends mostly on the fee attached relative to everyone else bidding for the same block space. Confirmations then accumulate on top. Each additional block multiplies the work an attacker would need to redo, so the number you require should scale with how much you would lose if the transaction were reversed.

#how-long-does-confirmation-take

A transaction is confirmed when it is inside a block other nodes have accepted. There is no moment at which it becomes mathematically irreversible — it just gets progressively more expensive to undo as blocks pile on top, because reversing it means redoing all that proof-of-work faster than the honest network extends the chain. "Confirmed" is a probability statement, not a switch.

See also: What is a 51% attack?

#what-is-a-confirmation

An unspent transaction output — a discrete chunk of coins your wallet can spend. Bitcoin has no account balance: what looks like one is the sum of outputs your keys control. Spending consumes whole outputs and returns the remainder to you as change. This is why a wallet holding many small outputs is expensive to spend when fees are high, since every input adds bytes and block space is what you pay for.

#what-is-a-utxo

Two different things share the name. A chain fork is a temporary disagreement about which valid block is the tip — normal, resolved within a block or two as one branch gains more work. A protocol fork is a rule change: a soft fork tightens the rules and stays compatible with old nodes, while a hard fork loosens them and splits the network unless everyone upgrades. A persistent split is what produces two coins with two separate histories.

#what-is-a-fork

A block that was valid but lost the race. Two miners can find valid blocks at almost the same moment; the network follows whichever branch accumulates more work and the loser’s block is discarded, so its miner earns nothing and its transactions go back to the mempool. Stale rates are a few percent on Bitcoin and higher on chains with shorter block times or slow propagation — which is why latency to your pool and your node matters more than miners usually think.

#what-is-a-stale-block

An attacker with more hash rate than everyone else combined can mine a private chain faster than the honest network and publish it, reorganising recent blocks to reverse their own transactions — double-spending to an exchange is the classic use. What it cannot do is take coins from your wallet, mint coins beyond the schedule, or spend coins whose keys it does not hold, because every node refuses those regardless of hash rate. On a large chain it is also self-defeating: acquiring the hardware moves the price against you and the loss of confidence damages the asset being attacked.

#what-is-a-51-percent-attack

No, and the confusion costs miners money. Hash rate measures how much work is being spent to secure a chain; price is what buyers and sellers agree a coin is worth. Rising hash rate often follows a rising price, because mining becomes worth funding, but the arrow usually runs from price to hash rate, not the reverse. Miners who bought hardware because hash rate was climbing have been badly hurt doing exactly that.

#does-a-higher-hash-rate-mean-a-higher-price

Nobody can break the cryptography to take your coins, and almost nobody needs to. Attacks go at the keys: phishing sites that ask for a seed phrase, clipboard malware that swaps a pasted payout address, fake browser extensions, or a compromised exchange. That last one matters most for a miner, because a pool payout address is a long-lived target — if malware swaps it, you may not notice for weeks. Verify the address in your miner configuration against your wallet, in person, periodically.

#can-someone-hack-my-wallet

Twelve or twenty-four words that encode the master secret a wallet derives all its keys from. Anything derived from those words can be recreated from them, so anyone who learns them owns the coins. Store it offline — written down or stamped in metal — not in a photo, a password manager, a chat message or a screenshot. Losing it means losing the coins, and no support desk can restore it.

See also: Can crypto be frozen or seized?

#what-is-a-seed-phrase

Self-custody cannot be frozen by anyone, and it also cannot be recovered by anyone — the same property seen from both ends. Coins held at an exchange or broker are entirely freezable, because what you hold there is a claim on a company, and that company obeys court orders and can also simply fail. Most people who lose access lose it to a lost seed phrase or a dead exchange, not to an attacker.

#can-crypto-be-frozen-or-seized

A hardware wallet, once the amount justifies one. Mining accumulates steadily and the payout address sits in a machine’s configuration for months, so it is worth keeping that address out of a hot wallet entirely: a hardware wallet lets you receive to an address whose keys are never on the miner or on a computer. Small balances on an exchange are convenient and fine; treating an exchange as storage is not.

#hardware-vs-hot-wallet

Lost keys, not theft. Coins are only spendable by whoever holds the private keys, so a lost seed phrase leaves them sitting on the ledger, visible to everyone and spendable by no one. Estimates of permanently lost supply run well north of a million BTC, mostly from the earliest years when BTC was worth nothing and backups seemed pointless. Pool payouts sent to an address whose key you no longer control are one of the small modern contributors.

#how-are-coins-actually-lost

A website that indexes the public chain so you can look up a transaction, address or block. It holds no keys and cannot move anything, so it is a read-only window. The privacy caveat matters: whatever you look up is logged by the operator, so checking your own payout address ties your IP to your mining income. If that concerns you, run your own node or use a client that fetches blocks directly.

#what-is-a-block-explorer

Every payment to the same address is linked on a public ledger, so reuse turns your transactions into one traceable history. Miners are the worst offenders here, because a pool payout address is typically configured once and never changed — which gives anyone watching a complete, dated record of your income. Use a fresh address for payouts when your pool supports it, and treat the one you have used as public.

#what-is-address-reuse

Not today, and the exposure is narrower than headlines suggest. Shor’s algorithm would break the elliptic-curve signatures that authorise spends, given a machine far larger than any that exists; the engineering gap is enormous. Coins in addresses whose public key has never been revealed on-chain are protected by a hash, which Shor does not help with. A migration to quantum-resistant signatures is a known and active area of work rather than a surprise. Treat confident claims in either direction as marketing.

#what-is-quantum-risk

No. Everything on this site is technical explanation and public data. There are no recommendations, no price targets and no return projections, and nothing here accounts for your circumstances. Mining carries the risk of losing everything you put in, and the fact that a mechanism is described accurately here says nothing about whether a purchase is a good idea for you. The calculator is arithmetic, not advice.

#is-this-financial-advice

The network table reads the SHA-256 entries from a public mining-statistics feed, and exchange prices come from a market data API. Both are refreshed on a schedule and cached, so what you see is a recent reading rather than a live socket. We store what the source reports and show when it was read, instead of implying the numbers tick continuously.

See also: Why does a hash rate say it changed days ago?

#where-do-hash-rates-come-from

Because that is the honest answer. A network hash rate is usually derived from difficulty rather than measured directly, and Bitcoin only retargets difficulty every 2,016 blocks — about two weeks. The number genuinely does not change most days, and a live-looking display would be theatre. We track when each value last actually moved, which is why some rows sit unchanged for a fortnight and then step.

See also: What is difficulty?

#why-does-hash-rate-say-changed-days-ago

It is a good model of the arithmetic, not a forecast. It uses live network difficulty, the chain height to derive the current subsidy, the coin price, and stock manufacturer hash rate and power figures. It excludes pool fees, cooling, downtime, hardware depreciation and the next difficulty retarget — every one of which makes reality worse than the model. Treat a marginal result as a warning rather than a green light, and measure your own rig’s real power draw with a meter before believing any figure on this site.

See also: How do I work out my break-even electricity price?

#how-accurate-is-the-calculator

It is the height and age of the most recently mined block, read from a node-backed API. It is on the page because it is the one number here that genuinely moves in real time — unlike a difficulty-derived hash rate, a new block really is a new fact every ten minutes on average. It also doubles as a liveness check: if the tip is hours old, something upstream is wrong rather than merely quiet. For a miner it is the clock their payouts are measured against.

#what-is-the-block-tip

From the public RSS and Atom feeds of a fixed, hand-picked list of crypto publishers. A scheduled job polls each feed, keeps the headline, a short excerpt, the link and the publication time, and discards everything else. Articles are never copied or rehosted — every entry links straight to the publisher, and a source that fails to answer shows up as stale rather than silently disappearing. The list is short on purpose: adding a feed means vouching for it.

#where-do-news-headlines-come-from

No. They are republished third-party data, they can be stale or wrong, and none of them are derived by us from the chain itself. Use them for orientation and check anything you are about to spend money on against the primary source — the manufacturer’s specification for a rig, the explorer for chain data, the exchange for price. Where a value here is an estimate rather than a measurement, the page says so.

#are-the-numbers-here-authoritative