Proof of Work
Experience Bitcoin mining firsthand. Hash data with SHA-256, adjust difficulty targets, and discover why proof-of-work is the backbone of Bitcoin's security.
How Mining Works
Input Data
A block header contains transactions, the previous block hash, a timestamp, and a nonce — a number miners can change.
Hash It
Run the data through SHA-256, a one-way function that produces a unique 64-character hexadecimal fingerprint.
Check Target
If the hash starts with enough leading zeros (below the difficulty target), the block is valid. Otherwise, increment the nonce and try again.
SHA-256 Hash Explorer
Change a single character and watch the entire hash change. This is called the avalanche effect— even the tiniest input change produces a completely different output.
Mining Simulator
Mine once to see time estimates for each difficulty
Exponential Difficulty
Each additional leading zero makes mining 16× harder. The number of attempts needed grows exponentially.
Your Browser vs The Bitcoin Network
YOUR BROWSER
Start mining to measure
BITCOIN NETWORK
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How Proof of Work Secures Bitcoin
Proof of work forces miners to expend real computational energy to add blocks to the chain. To reverse a transaction, an attacker would need to redo all the work from that block forward — plus outpace the rest of the network, which is performing quintillions of hashes per second.
The difficulty target automatically adjusts every 2,016 blocks (~2 weeks) to keep the average block time at 10 minutes, regardless of how much total hash power joins or leaves the network.
This elegant mechanism, described in the Bitcoin Whitepaper, creates a system where the cost of attacking the network always exceeds the potential reward. Learn more about the fundamentals on our Learn page.