Proof of
Work
The cryptographic consensus mechanism that powers Bitcoin — and the math behind why it's nearly impossible to cheat.
How PoW Works
Transactions Are Broadcast
When you send cryptocurrency, your transaction is broadcast to a peer-to-peer network of thousands of nodes. It sits in a shared waiting room called the mempool until a miner picks it up.
Miners Bundle Into a Block
Miners collect pending transactions and bundle them into a candidate block. The block includes a header with the previous block's hash, a timestamp, and a special field called the nonce.
The Hash Puzzle
Miners must find a nonce value that, when hashed with the block header, produces a result below a target number. There's no shortcut — you just keep guessing. Modern miners try billions of nonces per second.
Winner Takes the Reward
The first miner to find a valid nonce broadcasts the solved block. Other nodes instantly verify the solution and add it to their chain. The winning miner earns the block reward + transaction fees.
The key insight is asymmetry: finding the nonce is extremely hard, but verifying that someone found it is trivially easy — just hash the block once and check the result. This is the same principle behind a combination lock: impossible to crack by brute force in a reasonable time, but instantly openable with the right code.
The network automatically adjusts the difficulty target every 2,016 blocks (~2 weeks) to ensure a new block arrives approximately every 10 minutes, regardless of how much total hashing power joins or leaves the network.
The tamper-proof chain comes from chaining hashes: each block's header includes the hash of the previous block. Changing any historical transaction would change that block's hash, breaking every subsequent block — requiring attackers to redo all proof-of-work from that point forward while the honest chain keeps growing ahead of them.
Try It Live
Enter a transaction below, create a pending block, then start the mining simulation to watch the nonce increment until a valid hash is found.
Major PoW Networks
These blockchains use Proof of Work as their consensus mechanism, each with different hashing algorithms, block times, and use cases.
The original PoW blockchain, launched by Satoshi Nakamoto in 2009. Bitcoin defined proof-of-work for digital currency and remains the network with the highest hash rate and security. Mined using specialized ASICs.
Created in 2011 as the "silver to Bitcoin's gold." Litecoin uses the Scrypt algorithm, originally designed to be memory-intensive and resist ASIC mining. Offers 4x faster block times than Bitcoin.
Started as a meme in 2013, Dogecoin uses the same Scrypt algorithm as Litecoin, enabling merge mining — miners can mine both chains simultaneously. Has no supply cap, with 10,000 DOGE issued per block indefinitely.
A privacy-focused PoW chain using the Equihash algorithm, designed to be memory-hard. Zcash pioneered zk-SNARKs — zero-knowledge proofs that verify transactions without revealing sender, receiver, or amount.
The leading privacy-first blockchain, using RandomX — optimized for general-purpose CPUs and intentionally hostile to ASICs. Monero hides sender, receiver, and amount by default using ring signatures and stealth addresses.
A 2017 hard fork of Bitcoin focused on scaling on-chain by increasing the block size to 32MB vs Bitcoin's ~1MB. Uses the same SHA-256 algorithm, so Bitcoin ASICs can mine both. Aimed at everyday peer-to-peer payments.