A blockchain is a shared digital ledger that many independent computers keep identical copies of. New records are grouped into blocks, and each block carries a cryptographic fingerprint of the block before it, so any change to past entries is easy to detect and very hard to force through. On public blockchains, no single company runs the ledger.
What problem does a blockchain solve?
Most digital records live in a database run by one organisation. When you pay a friend through a banking app, no digital banknote moves: the bank edits two rows in its own ledger. That works because you trust the bank to keep accurate records, process the payment and not reverse it without a reason.
Digital money without such an operator ran into the double-spending problem. A digital file can be copied, so what stops someone spending the same coin twice? In 2008 the pseudonymous Satoshi Nakamoto proposed an answer in the Bitcoin whitepaper: announce every transaction publicly and have a network of nodes agree on one ordered history, secured by Proof of Work. The Bitcoin network went live in January 2009, and the data structure it used became known as a blockchain.
How does a blockchain work?
Every blockchain follows the same basic cycle, whatever the coin or network:
- A user signs a transaction with a private key, proving they control the funds without revealing the key.
- The transaction is broadcast to the network, and each node checks the signature and the balance against the shared rules.
- A block producer (a miner or a validator, depending on the network) bundles pending transactions into a block.
- A consensus mechanism decides which proposed block every node accepts next.
- Each node appends the block to its copy of the ledger, and the transaction gains confirmations as more blocks are built on top.
Our step-by-step guide to how a blockchain processes a transaction covers hashing, the mempool and fees in more detail.
Why is it called a "block chain"?
Each block holds a batch of transactions plus a header. In Bitcoin, the header includes the hash (a fixed-length fingerprint) of the previous block's header and a Merkle root that summarises every transaction in the block. Change one transaction in an old block and its Merkle root changes. That changes the block's hash, which breaks the link stored in the next block, and so on up to the newest block.
To make an altered history stick, an attacker would have to redo the work, or win the votes, for every block after the change and then overtake the honest network. That is why the US National Institute of Standards and Technology (NIST) describes blockchains as "tamper evident and tamper resistant" rather than strictly immutable. History can change in rare cases, such as a majority attack or a hard fork the community agrees to, but it cannot change quietly.
What are the key properties of a blockchain?
| Property | What it means | The caveat |
|---|---|---|
| Distributed | Many independent nodes hold full copies of the ledger; there is no single master server. | Copies are only as independent as the people running them. Hosting, mining or staking can still be concentrated. |
| Append-only | New blocks are added to the end of the chain; past entries are not overwritten. | A mistaken payment cannot be undone by an administrator. The recipient has to send the funds back. |
| Transparent | On public chains anyone can inspect every transaction with a block explorer. | Addresses are pseudonymous, not anonymous. Anyone who links an address to you can see its history. |
| Rule-based | Nodes reject any transaction or block that breaks the protocol rules. | Rules change through software upgrades, which need broad agreement among developers, node operators and users. |
| Programmable | Many chains run smart contracts that hold and move assets according to code. | Bugs in contract code can lock or lose funds. |
Who controls a blockchain?
Nobody owns a public blockchain such as Bitcoin or Ethereum in the way a company owns its database. NIST notes that permissionless networks are usually governed by a mix of users, block publishers and software developers, each with partial influence. Developers propose changes, node operators choose which software to run, and users decide which version of the chain they value.
Permissioned blockchains work differently: an owner or a consortium decides who may read the ledger and who may add blocks. Our comparison of public, private and consortium blockchains explains when each model makes sense.
Is blockchain the same as cryptocurrency?
No. Cryptocurrency was the first application, but a blockchain can record ownership of any digital token. Ethereum added a general-purpose computer, the Ethereum Virtual Machine, so blockchains now also run stablecoins, tokenised funds and gold, lending markets and multi-signature wallets. The benefits of blockchain are strongest where several parties who do not fully trust each other need one shared record.
When is a blockchain the wrong tool?
NIST's overview warns that many projects adopt blockchain out of fear of missing out. It lists signs that a blockchain may fit: many distributed participants, no trusted third party, transaction-based workflows, and a need for shared provenance or less manual reconciliation. If one trusted organisation already keeps the records, a conventional database is usually faster and cheaper. Our guide to blockchain limitations covers throughput, energy use and irreversible errors.
How Wealtii uses a blockchain: Wealtii's fund assets are held 1:1 in a Gnosis Safe 3-of-3 multi-signature vault on BNB Smart Chain. Because the vault address is public, anyone can check its holdings on a block explorer. The address and a BscScan link are on Wealtii's transparency page.
Frequently Asked Questions
What is a blockchain in simple terms?
A blockchain is a shared record book that many computers keep identical copies of. New entries are added in blocks, and each block is linked to the previous one by a cryptographic hash, so past entries cannot be quietly edited.
Can a blockchain be hacked or changed?
Rewriting confirmed history on a large public blockchain would require controlling most of its mining power or stake and outpacing the honest network, which is extremely expensive. Smaller networks have suffered these 51% attacks, and many crypto thefts target wallets, exchanges and apps rather than the underlying blockchain.
Who owns a public blockchain?
No individual or company owns a public blockchain such as Bitcoin or Ethereum. It is run by independent node operators using open-source software, and rule changes need broad agreement among developers, node operators and users.
Is blockchain only used for cryptocurrency?
No. Blockchains also record stablecoins, tokenised funds and commodities, supply-chain data and smart contracts. A blockchain helps most when several parties need to share one record without relying on a single trusted operator.
Sources & References
- Nakamoto, S. (2008) — Bitcoin: A Peer-to-Peer Electronic Cash System (accessed 21 Oct 2026)
- NIST IR 8202 — Blockchain Technology Overview (Yaga et al., 2018) (accessed 21 Oct 2026)
- Bitcoin Developer Guide — Block Chain (accessed 21 Oct 2026)
- ethereum.org — Blocks (developer documentation) (accessed 21 Oct 2026)
Disclaimer: This content is for educational purposes only and does not constitute financial, tax, or legal advice. Digital assets are volatile and carry risk of loss. Wealtii is early-stage and is not regulated by any financial authority.
