SHA-256 · Nonce search · Difficulty adjustment · Block rewards
This simulator shows how Bitcoin proof-of-work mining operates. Miners repeatedly hash a block header with different nonce values until the resulting hash begins with a required number of leading zeros (the difficulty target). The more zeros required, the harder it is to find a valid hash — exponentially more attempts are needed on average. When a miner succeeds, a new block is added to the chain and the miner receives a block reward (currently 3.125 BTC after the 2024 halving).
Bitcoin's difficulty adjusts every 2,016 blocks (~2 weeks) so that on average one block is found every 10 minutes, regardless of total network hashrate. As of 2025, the Bitcoin network computes over 700 exahashes per second — that's 700,000,000,000,000,000,000 hash operations every second. This simulator uses a simplified hash function for demonstration purposes.
This simulator models Bitcoin proof-of-work mining, the cryptographic process by which new blocks are added to the Bitcoin blockchain. Miners repeatedly compute SHA-256 hashes of a block header — varying a field called the nonce — until the resulting hash falls below a numeric target, which visually means it starts with a required number of leading zeros. The difficulty of this puzzle adjusts every 2,016 blocks so the network always produces roughly one block every 10 minutes, regardless of total computing power.
Bitcoin mining was first described in Satoshi Nakamoto's 2008 whitepaper and went live in January 2009. Today it secures a global network processing hundreds of billions of dollars in transactions, and the combined hashrate exceeds 700 exahashes per second — making it one of the largest distributed computing systems ever built.
Proof-of-work is a mechanism that requires miners to expend real computational effort before they can add a block to the blockchain. A miner must find a nonce value such that hashing the block header produces a hash below a set target. Because hash functions are one-way, the only practical method is brute-force trial — there is no shortcut, making the work verifiable but costly to produce.
Click Start Mining to begin the nonce search. Use the Difficulty slider to increase or decrease the number of leading zeros required — higher difficulty means exponentially more attempts on average. Increase the Miners slider to simulate competition between multiple miners racing to find the next block, and watch the blockchain canvas at the bottom grow as valid blocks are discovered.
Each additional leading zero required reduces the fraction of valid hashes by a factor of 16 (since hash digits are hexadecimal). With 4 leading zeros, roughly 1 in 65,536 hashes is valid; with 8 leading zeros, only about 1 in 4 billion. This exponential relationship means small difficulty increases translate into enormous jumps in the expected number of attempts before a block is found.
SHA-256 (Secure Hash Algorithm 256-bit) is a cryptographic hash function from the SHA-2 family, standardised by NIST in 2001. It produces a fixed 256-bit (64 hexadecimal character) output from any input, with the properties that tiny input changes completely alter the output (avalanche effect), and it is computationally infeasible to reverse the function or find two inputs with the same output. Bitcoin actually applies SHA-256 twice (double-SHA-256) for added security. This simulator uses a simplified hash function for performance, but the visual behaviour mirrors the real process.
Every 2,016 blocks — approximately two weeks at the target rate of one block per 10 minutes — Bitcoin nodes compare the actual time taken to mine those blocks against the 20,160-minute ideal. If blocks arrived faster than expected, difficulty increases; if slower, it decreases. The adjustment is capped at a factor of 4 in either direction per period, preventing extreme swings. This self-correcting mechanism has kept average block times close to 10 minutes since 2009 despite network hashrate growing by many orders of magnitude.
When a miner successfully mines a block they earn the block reward — newly created Bitcoin — plus all transaction fees from the transactions included in that block. The block reward started at 50 BTC in 2009 and halves every 210,000 blocks (roughly every four years) in an event called the "halving." After the April 2024 halving it stands at 3.125 BTC. The total supply is capped at 21 million BTC, which will be reached around the year 2140, after which miners will depend entirely on transaction fees.
No. Bitcoin uses double-SHA-256, which is ASIC-friendly and has led to highly specialised mining hardware dominating the network. Other cryptocurrencies deliberately chose different algorithms: Litecoin uses Scrypt (originally designed to be memory-hard), Monero uses RandomX (optimised for general-purpose CPUs), and Ethereum used Ethash before switching to proof-of-stake in 2022. Each algorithm reflects different priorities around decentralisation, hardware accessibility, and energy efficiency.
The proof-of-work concept was first proposed by Cynthia Dwork and Moni Naor in 1993 as a way to deter email spam, and the term "proof of work" was coined by Markus Jakobsson and Ari Juels in 1999. Satoshi Nakamoto adapted and combined these ideas with Adam Back's Hashcash system (1997) to create Bitcoin's consensus mechanism, publishing the Bitcoin whitepaper in October 2008 and mining the genesis block on 3 January 2009.
Bitcoin mining connects to several broader topics: cryptographic hash functions underpin all blockchain security; game theory explains miner incentives and why honest mining is the dominant strategy (the selfish-mining attack aside); network economics govern mining pool formation; and thermodynamics limits efficiency since all hashing work ultimately dissipates as heat. Related simulations on this site include financial bubble dynamics, stock price models (GBM), and options pricing — all exploring how complex emergent behaviour arises from simple rules in economic systems.
Modern Bitcoin mining uses Application-Specific Integrated Circuits (ASICs) — chips designed exclusively to compute double-SHA-256 as fast and efficiently as possible. Leading ASICs in 2024-2025 achieve over 200 terahashes per second (TH/s) at roughly 20 joules per terahash, a many-million-fold efficiency improvement over the CPU mining used in 2009. Miners typically join pools to smooth out revenue, sharing rewards proportional to contributed hashrate. Industrial mining farms now consume as much electricity as some small countries, driving ongoing debate about renewable energy integration.
Active research areas include: selfish-mining attacks, where a pool with sufficient hashrate can earn disproportionate rewards by strategically withholding blocks; fee-only security, studying whether transaction fees alone will provide adequate mining incentives once block rewards approach zero; the long-range attack problem for newly syncing nodes; and the environmental economics of proof-of-work versus proof-of-stake. Cryptographers also study whether quantum computers could eventually break SHA-256's one-wayness, though current estimates place a practical quantum threat many decades away.