Definition
A distributed, immutable digital ledger that records transactions in blocks. Each block is cryptographically linked to the previous one, forming a secure chain.
In depth
A blockchain is a specific type of distributed database where data is grouped into "blocks" and linked chronologically using cryptographic hashes. Each block contains a hash (fingerprint) of the previous block — altering any historical block would invalidate every subsequent block, requiring computational work across the entire chain. On an established public network, this is practically infeasible, making blockchains effectively immutable.
Unlike traditional databases controlled by a single company, a public blockchain is replicated identically across thousands of independent nodes worldwide. No single party controls the authoritative copy — all participants verify transactions independently against the same shared rules. This combination of immutability and decentralization is the core security property that makes blockchains valuable for high-stakes record-keeping.
Blockchain technology underpins all cryptocurrencies, but its applications extend far beyond finance. Supply chain provenance, healthcare record sharing, digital identity verification, land title registration, voting systems, and intellectual property tracking are among the industries deploying blockchain solutions.
There are three main blockchain architectures: public (permissionless — anyone can participate, like Bitcoin and Ethereum), private (permissioned, controlled by a single organization, like Hyperledger Fabric used by enterprises), and consortium (governed jointly by a group of organizations). Each makes different trade-offs between transparency, transaction speed, privacy, and degree of decentralization.
Frequently asked questions
Is blockchain the same as Bitcoin?
No. Blockchain is the underlying data structure and technology; Bitcoin is one specific application built on it. Many independent blockchains exist — Ethereum, Solana, Polygon, Avalanche, and thousands more — each with different design goals. Bitcoin runs on its own dedicated blockchain.
Can data on a blockchain be deleted or changed?
In practice, no. Altering historical data on an established public blockchain would require controlling 51% or more of the total network computing power — economically prohibitive for large networks like Bitcoin or Ethereum. On smaller chains with fewer participants, '51% attacks' have occurred.
Are all blockchains public and transparent?
No. Private and consortium blockchains restrict who can read and write to them. Many enterprises run private blockchains for internal record-keeping, supply chain management, or interbank settlements — where full public transparency isn't desired. Privacy-focused public blockchains like Monero and Zcash also obscure transaction details from public view.
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