What Is Blockchain? Explained Without the Jargon

A blockchain is a record book that thousands of computers keep identical copies of. Instead of one company holding the master copy — the way Safaricom holds your M-Pesa statement — everyone in the network holds it, checks it and adds to it by the same rules. Records are grouped into “blocks”, and each block is chained to the one before it, which is where the name comes from.

Blockchain in one picture: a shared M-Pesa statement

Imagine every M-Pesa user in Kenya holding a copy of one giant statement listing every payment ever made. When Akinyi sends Otieno KSh 1,000, the payment is announced to everyone, and every copy is updated together. If someone tried to edit their copy to show they had received KSh 100,000, the thousands of other copies would disagree, and the fake version would be rejected.

That is the core idea of a blockchainBlockchainA shared public record of transactions that many computers keep identical copies of, so no single company can quietly edit it. Glossary. It solves a specific problem: how strangers who do not trust each other can agree on who owns what, without a bank or Safaricom in the middle. For digital money this matters, because a digital file can normally be copied — and money that can be copied is worthless.

The trade-off is efficiency. One company updating one database is far faster and cheaper than thousands of computers checking every entry. A blockchain only makes sense when removing the central record-keeper is worth that cost.

What is inside a block

A block is a batch of records plus a small header that links it to the chain. On Bitcoin, a new block is added roughly every ten minutes; other blockchains produce blocks every few seconds.

Each payment inside is identified by a transaction IDTxID (transaction hash)A unique receipt number for a blockchain transfer. Paste it into a block explorer to see whether the transfer arrived. Glossary, and anyone can look it up on a block explorerBlock explorerA public website (such as Tronscan or Etherscan) that shows every transaction on a blockchain. Glossary — a public website that shows every block and transaction. This openness is why exchanges ask for a TXID when a deposit goes missing: it proves exactly what happened on the chain.

Hashes: the digital fingerprint that makes tampering obvious

A hash is the output of a maths function that turns any data into a fixed-length string of characters. Bitcoin uses one called SHA-256. The same input always gives the same output, but changing even one character gives a completely different result. Here is a real example we ran:

One digit changed, and the fingerprint is unrecognisable. Now remember that every block stores the hash of the previous block. If someone altered a payment in an old block, that block’s hash would change, which would break the link stored in the next block, and the next, all the way to the latest one. Every honest computer would instantly see that the chain no longer adds up.

How strangers agree: consensus

Linking blocks with hashes makes tampering obvious, but someone still has to decide which new block gets added next. The rules for that decision are called consensus. The two you will hear about most are proof of work and proof of stake.

1. A payment is broadcast

   Your walletCrypto walletAn app or device that holds the keys to your crypto. The coins stay on the blockchain; the wallet proves they are yours. Glossary signs the payment with your private key and sends it to the network. Computers check that the signature is valid and that you actually have the funds.

2. Someone proposes a block

   In proof of work, minersMiningUsing computers to secure the Bitcoin network in exchange for newly created bitcoin and fees. Glossary compete to solve a puzzle; the winner proposes the block. In proof of stake, a validator with coins locked up as a deposit is selected to propose it.

3. The network checks it

   Every node verifies the block against the rules — valid signatures, no double-spending, correct reward. Invalid blocks are rejected, whoever made them.

4. The chain grows

   The accepted block is added to every copy of the ledger. Each new block on top adds a confirmationConfirmationEach new block added after your transaction. Exchanges credit deposits after a set number of confirmations. Glossary and makes reversing earlier payments harder.

Ethereum switched from proof of work to proof of stake in an upgrade called the Merge on 15 September 2022. The Ethereum Foundation estimates this cut the network’s energy use by about 99.95%. Bitcoin has kept proof of work, and its supporters argue the energy cost is exactly what makes its history so expensive to rewrite. If you want to understand Ethereum itself, see our Ethereum coin page.

Public, private and permissioned blockchains

Not every blockchain is open to the world. The ones behind cryptocurrencies are public, but companies and governments often prefer versions where only approved members can write records.

Private and permissioned chains are faster and can keep data confidential, but you have to trust whoever runs them — which removes much of what makes a public blockchain special. Critics argue that many “blockchain” projects would work just as well as an ordinary database. That is a fair question to ask of any pitch.

Real Kenyan uses beyond crypto

Kenya has had more blockchain announcements than working systems, so we only list examples we could verify, and we say where the trail runs out.

Sarafu community currencies. Grassroots Economics, a Kenyan non-profit, has run community currency programmes since 2010, starting with paper vouchers in places such as Kilifi County. Since 2018 its Sarafu vouchers have been issued as tokensTokenA crypto asset that runs on top of another blockchain, for example USDT on the TRON network. Glossary on a public blockchain (today the Celo network), and members can use them on basic feature phones through USSD. Small businesses and self-help groups trade the vouchers for goods and services when shillings are scarce. The organisation has worked with the Red Cross and other aid agencies.

Microloans for food kiosks. In 2018, IBM Research Africa and Twiga Foods ran a pilot that offered small loans to Nairobi kiosk owners by SMS when they ordered stock. The pilot covered about 220 retailers, with an average loan of around US$30, and recorded the lending process on a permissioned blockchain built with Hyperledger Fabric. We found no evidence of a large-scale rollout after the pilot.

Government land records. In 2018 the Ministry of ICT set up a Distributed Ledgers and Artificial Intelligence taskforce chaired by Dr Bitange Ndemo. Its recommendations included automating land records and creating a single source of truth for land ownership, along with uses in fighting fraud and counterfeits. We found no public evidence that a national blockchain land registry has since gone live, so treat claims that “Kenya’s land registry runs on blockchain” with caution.

Blockchain and crypto conferences in Kenya

Nairobi has become a regular stop for Africa’s crypto community. The Africa Bitcoin Conference held its third edition at the JW Marriott in Nairobi on 9–11 December 2024, with Block co-founder Jack Dorsey among the speakers; the organisers reported around 800 attendees. People also search for a “Kenya Blockchain and Crypto Conference”, but we could not confirm a single recurring event under that exact name, so check the organiser’s official site, ticketing page and past editions before paying for any event — fake conference tickets and “VIP investment sessions” are a known trick.

What blockchain cannot do

It cannot reverse mistakes. Send USDT to a wrong address and no help desk can pull it back. It cannot stop you being tricked: most Kenyan crypto losses happen through fake agents, phishing links and P2P scams, not broken blockchains. And it does not make a project legitimate — a token can live on a perfectly secure chain and still be worthless.

What it does well is narrower and still useful: a public record that nobody controls, that anyone can check, and that has proved very hard to rewrite.

Where to go next

Now that you know how the ledger works, read what is Bitcoin to see the first and largest blockchain in action, or what is cryptocurrency for how coins and tokens differ. When you move from theory to practice, our wallet guide explains keys and seed phrases, and the glossary explains every term on this page in plain English. All our explainers are collected on the Learn hub.