- A blockchain is a shared record that many computers keep in sync, so no single party controls it.
- It is useful for some problems, but it is not the answer to everything.
- Never treat a blockchain headline as proof that an investment or scheme is safe.
The short answer
A blockchain is a type of database that is shared across many computers. Instead of one company keeping the records, many participants hold identical copies and agree on every new entry. New records are grouped into blocks, and each block is linked to the one before it, forming a chain. Because changing an old block would break every block after it, the history becomes very hard to tamper with.
A simple analogy
Imagine a village notebook that records who paid whom. Instead of one person guarding it, every household holds a copy. When someone adds a line, the households compare notes and only accept it if most copies agree. If one person secretly changes an old line in their own copy, the others notice at once because their copies no longer match. A blockchain works on the same idea, with software doing the checking.
How it works step by step
- A transaction is made. For example, one person sends digital money to another.
- It is broadcast. The request is sent to computers on the network.
- It is checked. The computers confirm that the sender has the funds and the right to send them.
- It joins a block. Verified transactions are grouped into a block.
- The network agrees. The participants use a rule, called a consensus mechanism, to accept the block.
- The block is chained. It is linked to the previous block with a digital fingerprint called a hash, and the update spreads to every copy.
Public and private blockchains
| Type | Who can join | Example use |
|---|---|---|
| Public | Anyone | Cryptocurrencies such as Bitcoin |
| Private | Approved members only | Company record-keeping and supply chains |
Bitcoin, the first major blockchain, was introduced in 2009 by a person or group using the name Satoshi Nakamoto. Many other blockchains have appeared since.
Consensus: how the network agrees
- Proof of work: computers compete to solve a puzzle, which uses a lot of electricity. Bitcoin uses this.
- Proof of stake: participants lock up coins as a pledge to validate blocks, which uses far less energy.
What blockchain is good for
- Moving digital money without a bank in the middle.
- Tracking goods through a supply chain, where many companies need to trust the same record.
- Keeping tamper-evident records, such as certificates or ownership history.
- Automating agreements with smart contracts, which are small programs that run when conditions are met.
Limits and risks
Blockchains are slower and more costly than ordinary databases for most tasks. If one trusted organisation can safely keep the records, a normal database is simpler and cheaper. The technology also does not make people honest. Scams, fake tokens and promises of guaranteed profit are common around cryptocurrency.
- If a message promises guaranteed returns, treat it as a warning sign.
- Never share your wallet’s recovery phrase or private key with anyone.
- Be wary of unknown links and fake wallet apps. Read our guide to fake apps and malware and to phishing emails and SMS scams.
Quick checklist
- Remember that a blockchain is a shared record, not a magic investment
- Ask whether a normal database would do the job
- Never share recovery phrases or private keys
- Distrust guaranteed returns
- Do your own research and consider professional advice before investing
Key points to remember
Blockchain is a clever way to share records without a central keeper, and it is useful in specific cases. This guide is general information and not financial advice. For protecting your accounts, set up a password manager and two-factor login.
