A blockchain is a shared database that stores data in blocks, links each block to the one before it with a cryptographic hash, and is kept in sync by thousands of independent computers, so no single party can change past entries. The best-known blockchain is Bitcoin (BTC): its first block was mined on 3 January 2009, and on 11 November 2026 it had reached block 975,389, according to mempool.space. Each new block holds thousands of transactions and points back to its predecessor, all the way to that first block.
Blockchain at a glance
- Bitcoin today: the last ten blocks held 4,739 transactions and 1.47 MB each on average (mempool.space, 11 November 2026).
- Speed: a new Bitcoin block arrives about every 10 minutes, as the Bitcoin white paper planned; Ethereum (ETH) works in 12-second slots.
- Security: Bitcoin miners computed about 958 exahashes per second, that is 958 quintillion attempts every second.
- Energy: since switching to proof of stake in 2022, Ethereum uses more than 99.988% less electricity (ethereum.org).
- Money on chain: $291.7 billion in stablecoins and $77.5 billion in DeFi run on blockchains (DefiLlama).
- Throughput: 4,739 transactions per block every 10.7 minutes means about 7.4 Bitcoin transactions per second.
What is Blockchain?
Blockchain is a revolutionary technology that allows the recording of transactions on a distributed ledger. It's the foundation of cryptocurrencies like Bitcoin and Ethereum but extends far beyond them. Essentially, a blockchain is a chain of blocks, where each block contains a list of transactions. These blocks are linked and secured using cryptography, forming a tamper-evident and tamper-resistant chain.
The decentralized nature of blockchain means that it doesn't rely on a central point of control. Instead, it uses a peer-to-peer network where each participant (node) has a copy of the ledger, ensuring transparency and security. This makes blockchain an ideal solution for situations where trust is an issue or where centralized control poses a risk.
How Does Blockchain Work?
Blockchain's functioning can be broken down into several key steps:
- Transaction Initiation: A user initiates a transaction, which could involve cryptocurrencies, contracts, records, or any digital data.
- Block Creation: Once a transaction is initiated, it's grouped with other transactions to create a new block.
- Validation: Network nodes validate the transaction using algorithms. This process is known as mining in some blockchains like Bitcoin.
- Hashing and Linking: Each block is given a unique hash (a cryptographic fingerprint) and includes the hash of the previous block, thus linking them.
- Adding to the Ledger: Once validated, the block is added to the blockchain, and the transaction is completed.
Why is Blockchain Important?
Blockchain technology represents a paradigm shift in how information is gathered and communicated. It provides a secure and transparent way to record transactions and manage data. The implications are vast and include:
- Enhanced Security: The decentralized and cryptographic nature of blockchain makes it secure against tampering and fraud.
- Increased Transparency: With blockchain, all transactions are visible to all participants, ensuring unparalleled transparency.
- Reduced Costs: By eliminating intermediaries, blockchain reduces transaction costs and complexities.
- Improved Efficiency: Blockchain automates and streamlines processes, leading to faster and error-free transactions.
Applications of Blockchain
Blockchain's potential extends across various sectors:
- Cryptocurrencies: Digital currencies like Bitcoin and Ethereum.
- Smart contracts: Self-executing contracts with the terms directly written into code.
- Supply Chain Management: Enhancing transparency and traceability.
- Banking and Finance: For secure and efficient transactions.
- Healthcare: Managing medical records securely and efficiently.
- Voting Systems: Ensuring secure and tamper-proof electoral processes.
- Intellectual Property: Protecting and managing digital rights.
Advanced: What is the Blockchain data structure?
The blockchain data structure is explained as a back-linked record of blocks of transactions, which is ordered. It can be saved as a file or in a plain database. Each block can be recognized by a hash, created utilizing the SHA256 cryptographic hash algorithm on the header of the block. Each block mentions a former block, also identified as the parent block, in the "previous block hash" field, in the block header. Let's first look at each term more closely.
Index: This term symbolizes the location of the block inside the blockchain. The first block is indexed '0', the next '1', and so on.
Hash: Hash is the function that facilitates the rapid classification of data in the dataset
Previous hash: Each and every block in the blockchain data structure, is associated with its ancestors. This characteristic adds to its immutability as a variety in the order of blocks.
numTx: This wares a tally of the number of transactions enumerated in the block.
Timestamp: It saves the time aspects of when the block was built.
Nonce: It saves the integer (32 or 64bits) that are utilized in the mining method.
Transaction: This is a different track saved as arrays in the frame of the block. They save the specific version of a transaction executed so far in the block.
Merkle Tree: A Merkle tree, also perceived as a binary hash tree, is a data structure utilized for efficiently compiling and validating the uprightness of large sets of data.
What is a Block?
A block is a package data structure. According to Bitcoin Book, a block is a container data structure that clusters transactions for incorporation in the public ledger known as the blockchain.
Block details
The block is composed of a header that includes metadata, accompanied by a lengthy record of transactions that advance its size. The block header is 80 bytes and the common transaction is at least 400 bytes. The common block includes more than 1900 transactions. A complete block, with all transactions, is almost 10,000 times greater than the block header. These figures come from an earlier edition of the book; in November 2026, the last ten Bitcoin blocks held 4,739 transactions and 1.47 MB on average, according to mempool.space.
What is the Block Header?
The block header is made up of metadata (Data about data).
The Block Header Details
The first part: There is a citation to a former block hash, which joins this block to the earlier block in the blockchain.
The second part: In this, metadata such as timestamp, and nonce correlate to the mining race.
The third part: In this metadata is the Merkle tree root. This tree root is a data structure that is utilized to efficiently compile all the transactions in the block.
The Block Identifiers
There are two ways the blocks can be identified. These are cryptographic hash and block height.
The primitive identifier of a block is its cryptographic hash. It is also known as a digital fingerprint which is built by hashing the block header twice through the SHA256 algorithm. The resulting 32-byte hash is described as the block hash but is more precisely the block header hash because is utilized to calculate it. For example, 000000000019d6689c085ae165831e934ff763ae46a2a6c172b3f1b60a8ce26f is the block hash of the first bitcoin block ever created. The block hash recognizes a block and can be autonomously determined by any node by directly hashing the block header.
Another way to recognize a block is by its location in the blockchain. This is described as the block height. The first block created is at block height 0 (zero) and is the same block that was earlier cited by the next block hash is 000000000019d6689c085ae165831e934ff763ae46a2a6c172b3f1b60a8ce26f.
What is the Genesis Block?
The first block in the blockchain is known as the genesis block. This was built in the year 2009. It is the universal parent of all the blocks in the blockchain. In other words, if people begin at any block and follow the chain backward, they will ultimately arrive at the genesis block.
Every node perpetually begins with a blockchain of at least one block because the genesis block cannot be modified. Every node always recognizes the genesis block's hash and structure. It also recognizes its fixed time when it was created and even its single transaction. Thus, every node has the starting point for the blockchain, a secure "root" from which to build a trusted blockchain.
Types of Blockchain Networks: Public, Private, Consortium and Hybrid
Not every blockchain network is open to everyone. The four types differ in who may join, read the ledger and validate transactions:
| Type | Who can join and read | Examples and uses |
|---|---|---|
| Public (permissionless) | Anyone can read, send transactions and help validate | Bitcoin, Ethereum, Solana |
| Private (permissioned) | One organization decides who participates | Internal settlement and record systems of companies |
| Consortium | A group of organizations runs the network together | Trade finance and supply chain networks of several firms |
| Hybrid | Private data with proofs anchored on a public chain | Tokenized assets and registries |
Public blockchain networks
A public blockchain has no access restrictions: anyone can run a node, send transactions and help validate new blocks. Bitcoin and Ethereum are public blockchains. They are the most decentralized, but every transaction record is visible to all.
Private blockchain networks
A private blockchain is run by one organization that decides who joins and who sees which data. Companies use private blockchain networks for internal records where they want a tamper-evident log without making data public.
Consortium blockchain networks
In a consortium blockchain network, a group of preselected organizations, for example several banks or trading partners, share control. The network members validate transactions together, which suits a business network in which no single company should own the ledger.
Hybrid blockchain networks
Hybrid blockchains keep data private but anchor proofs on a public chain, so outsiders can verify that records were not changed without seeing their content.
Consensus: Proof of Work vs. Proof of Stake
A blockchain needs a rule for who may add the next block. The two main consensus mechanisms differ in what they put at stake:
| Proof of work (Bitcoin) | Proof of stake (Ethereum) | |
|---|---|---|
| Who adds blocks | Miners who find a valid hash first | Validators chosen at random, weighted by staked ETH |
| What secures it | Computing power: about 958 EH/s on 11 November 2026 | Staked coins that can be cut (slashed) for cheating |
| Block rhythm | Target 10 minutes; recent average 10.7 minutes | One slot every 12 seconds, 32 slots per epoch |
| Energy use | High, by design | More than 99.988% lower than Ethereum's former proof of work |
Sources: mempool.space, ethereum.org on proof of stake. Our guide on how to stake crypto explains how proof of stake pays validators and stakers.
Distributed Ledger Technology and Public Key Cryptography
A blockchain is one kind of distributed ledger technology: every node stores a full copy of the ledger and checks new transactions against it. Ownership is proven with cryptographic keys. Each user holds a private key, which signs transactions, and a public key, from which the address is derived. Anyone can check a signature with the public key, but only the holder of the private key can create it. The hashes that link the data blocks make the blockchain an immutable record: changing an old transaction would change its block's hash and break the link to all subsequent blocks. Our guide on how to store crypto explains how to keep private keys safe.
Bitcoin Mining: How a New Block Joins the Bitcoin Blockchain
On the Bitcoin blockchain, miners collect new transactions from the network, build a candidate block and change its nonce until the block header's hash falls below a target set by the network difficulty. The first miner to find such a hash broadcasts the new block; the other nodes check it and build on top of it. The winner receives the block subsidy plus the transaction fees. Since the halving in April 2024, the subsidy is 3.125 bitcoin per block, and it halves every 210,000 blocks. The next halving is due at block 1,050,000: 74,611 blocks after block 975,389, which at the recent pace of one block every 10.7 minutes means about 557 days, in spring 2028 by our calculation.
Blockchain Protocols and Blockchain Platforms
A blockchain protocol is the set of rules every node follows. Public blockchain platforms differ in speed, fees and what developers can build:
- Bitcoin (BTC): focused on digital currency and security; simple scripts, no general smart contracts.
- Ethereum (ETH): the leading platform for smart contracts, DeFi and tokens; many layer-2 networks build on it.
- Solana (SOL): a high-speed blockchain for trading, payments and consumer apps.
- Enterprise platforms: permissioned frameworks for private and consortium networks; cloud providers also offer them as managed blockchain services.
How Industries Use Blockchain Applications
- Finance: financial institutions use blockchain for payments, settlement and tokenized funds; stablecoins carry digital dollars around the clock.
- Supply chain management: companies record each step of a product's journey, so buyers can trace origin and handling.
- Healthcare: medical records and drug supply chains can be logged so changes are traceable.
- Public sector: registries for land, companies or certificates use blockchain as a shared, tamper-evident record.
- Compliance: because public ledgers are transparent, analytics firms trace stolen funds and money laundering across blockchains.
Why Companies Use Blockchain Technology
Companies use blockchain technology when several parties need to record transactions in one shared blockchain ledger without a central authority. A blockchain system replaces the reconciliation of separate databases: every network member sees the same transaction data, and the immutable record shows who changed what and when. Financial institutions use blockchain for financial transactions such as cross-border payments and the settlement of digital assets, retailers use blockchain to trace goods through the supply chain, and insurers use blockchain to share claims data. Smart contracts automate the next step, for example a payment that is released when a delivery is confirmed.
Blockchain services: blockchain technology as a service
Not every company builds its own blockchain network. Cloud providers offer blockchain services that run the underlying software, so a firm can test blockchain applications without operating its own nodes. A blockchain implementation still needs a clear blockchain strategy: which partners join, which data is stored on chain, and who pays the additional costs for nodes and integration.
Digital currency and digital assets
Public blockchains made a new kind of digital currency possible. Bitcoin was the first; today, stablecoins, tokenized funds and other digital assets use blockchain technology to move value over a global computer network around the clock. Each holder controls them with a pair of private and public keys instead of an account at a bank.
When blockchain technology is the wrong tool
If one organization controls all the data and trusts its own database, a blockchain adds cost without benefit. Blockchain technology pays off where trust between parties is low and a shared, tamper-evident record saves work. Before you use blockchain, ask who needs to write to the ledger and whether they trust a single operator.
Blockchain vs. a Traditional Database
| Public blockchain | Traditional database | |
|---|---|---|
| Control | No single owner; thousands of nodes hold a copy | One administrator |
| Changing past data | Practically impossible without redoing the work or stake behind later blocks | Possible for the administrator |
| Speed and cost | Slower, with fees per transaction | Fast and cheap |
| Best for | Shared records between parties who do not trust each other | Data one organization controls |
Blockchain Use Cases in 2026: What Runs On Chain Today
- Money: Bitcoin is worth about $1.48 trillion (CoinMarketCap, 11 November 2026), and $291.7 billion in dollar stablecoins move over blockchains.
- Decentralized finance: $77.5 billion are locked in lending, trading and staking apps; see our DeFi guide.
- Tokenized assets: real-world asset protocols such as tokenized treasuries held $3.6 billion according to DefiLlama's RWA category.
- Digital ownership: NFTs and Bitcoin inscriptions; see our NFT guide and the Bitcoin Ordinals guide.
- Supply chains and records: companies anchor proofs of origin, certificates and documents on chain.
Limits of Blockchain Technology
Blockchains trade speed for trust. Bitcoin processes about 7.4 transactions per second on its base layer, by our calculation from the recent blocks, far fewer than a card network. Fees rise when blocks are full, data on a public chain is visible to everyone, and a lost private key cannot be recovered. Layer-2 networks, faster blockchains and careful wallet security address these limits, but each comes with its own trade-offs.
How to Explore a Blockchain Yourself
You do not need to run a node to look inside a blockchain. A block explorer such as mempool.space for Bitcoin shows every block, its hash, the previous block hash, its transactions and fees. Search for any transaction ID or address, and you can follow coins from block to block. Our list of the best crypto tools includes explorers for other blockchains.
Blockchain FAQ
Rudy Fares
Equity Trader, Financial Consultant, Musician and Blockchain Aficionado. I spend my time doing Technical and Fundamental Analyses for Stocks, Currencies, Commodities and Cryptocurrencies.