Blockchain
A shared digital ledger that records transactions in linked batches, copied across many computers and hard to alter.
A blockchain stores data in blocks that each reference the one before, forming a chain back to the first record. Change an old block and every later hash breaks, so tampering is obvious. Thousands of nodes hold copies and check each other, which is what makes the record hard to rewrite.
Bitcoin launched the first working version in 2009. The same design now underpins Ethereum, Solana, and most crypto. No single company runs it; the network agrees on what's true through a consensus mechanism.
Related terms
A batch of transactions bundled together, time-stamped, and cryptographically linked to the block before it.
Distributed Ledger Technology (DLT)The broad category of systems that keep a synchronized record across many sites with no central master copy.
Consensus MechanismThe rules a decentralized network follows to agree on one valid history without trusting any central party.
DecentralizationSpreading control and data across many independent participants so no single party can dictate or shut things down.