The visual guide

Understanding blockchain and Bitcoin, explained in 3D

A ledger that everyone keeps at the same time, and that nobody can forge. Seven animated steps to understand the nodes and their vote, mining, decentralised storage and what blockchain brings to artificial intelligence.

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20,000+: nodes keeping the ledger
10 min: between two blocks, since 2009
3.125 BTC: reward per block found
35 W: are enough to mine at home

Guided tour

The blockchain in seven steps

Every step animates: send a transaction, try to cheat, edit an old block, cut storage nodes, and watch the network react.

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Step 1 / 7

A ledger with no owner

A bank keeps its ledger in a single computer. Bitcoin copies it onto tens of thousands of machines spread across the planet. Every copy holds every transaction since 3 January 2009.

There is no central server to hack, bribe or unplug.

The ledger weighs more than 700 GB and grows by almost 2 MB every ten minutes. Anyone can download a full copy and check it block by block from the very first one, without asking permission: that is what a full node (Bitcoin Core) does.

Step 2 / 7

Bank or blockchain: who keeps the account?

When you pay by card in a shop, your money does not go to the merchant. The terminal asks the merchant's bank, which asks the card network, which asks your bank: it is your bank, in its own server, that decides within two seconds whether the line "– €40" gets written on your account. The merchant only sees the money one to three days later, minus the fee. Every intermediary keeps its own ledger, and each can block, reverse or charge.

On a blockchain there is no bank server: the ledger is the chain itself. Your wallet signs the transaction, the nodes check it, a miner writes it into a block, and the merchant owns it, without going through anyone.

The bank keeps your balance in its database and can change it. The chain keeps the full history, and nobody can change it.

Card circuit: cardholder → terminal or point-of-sale software → acquiring bank → network (Visa, Mastercard, national schemes) → issuing bank. Authorisation comes back in 1 to 3 seconds, but it is only a promise: clearing and interbank settlement happen overnight, and the money reaches the merchant on D+1 or D+2. Three parties take a cut (interchange, network, acquirer), 0.5 to 2% of the amount depending on the card, and the payment can be disputed for months (chargeback).

Bitcoin circuit: the wallet signs with the private key, the transaction is broadcast to the nodes, which check the signature and the absence of double spending, then it waits in the queue (mempool) for a miner to include it. One confirmation in ten minutes on average, six for a large amount; after that it is final, with no reversal possible. The fee goes to the miner and is chosen by the sender according to urgency. For small instant payments, the Lightning network settles off-chain and only writes the final balance.

The fundamental difference: a bank keeps balances in a database it administers; Bitcoin only keeps transactions, and the balance is recomputed by replaying the history since 2009, which every node does.

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Blockchain in one sentence

A blockchain is a ledger that thousands of computers keep at the same time, in which you can only add pages, never change one. Bitcoin is the first application of this idea: a ledger of transactions open to everyone, with no bank or central authority, running without interruption since 3 January 2009.

The nodes: who keeps the ledger

A node is a computer that keeps a full copy of the ledger and checks every transaction and every block against the protocol rules. There are more than 20,000 of them worldwide, run by individuals, companies and associations. None has more power than another. When a transaction arrives, each node checks that the bitcoins exist, that they really belong to the signer and that they have not already been spent. A transaction or a block that breaks the rules is rejected, whoever sent it. This permanent "vote" is what replaces trust in an institution.

Centralised bank or blockchain: the same payment, two circuits

A card payment goes through five parties before it reaches the merchant: the terminal or point-of-sale software, the merchant's acquiring bank, the card network, then your issuing bank, whose server is the only one allowed to write "– €40" on your account. Authorisation takes two seconds, but the real money is only paid out on D+1 or D+2, after clearing, and each party takes its share. On a blockchain, the chain of blocks plays the role of the bank's server: it holds the whole history and every transaction, but no party owns it.

	Bank and card	Blockchain (Bitcoin)
Who keeps the ledger	The bank, in its own server; one copy per bank, invisible to you	More than 20,000 nodes, each with the full history, readable by all
What is stored	Balances, which the bank can change, freeze or correct	Transactions; the balance is recomputed by replaying the history
Intermediaries	Terminal, acquirer, card network, issuer	None: the wallet signs, the nodes check, a miner writes
Delay	Authorisation in 2 s, money at the merchant on D+1 or D+2	One confirmation in 10 min on average, six for a large amount; instant via Lightning
Fees	0.5 to 2% of the amount, shared between three parties	Chosen by the sender, paid to the miner, independent of the amount
Reversal	Chargeback possible for months	Final after confirmation
Availability	Opening hours, limits, allowed countries, account that can be closed	24/7 since 2009, no permission or account needed
Point of failure	The server of the bank or of the network	None: the majority of nodes would have to be switched off

Neither is "better" everywhere: the card offers recourse in a dispute and the customer identification the law requires; the blockchain offers finality, openness and no trusted third party. Understanding what the chain replaces, the bank's server, is the key to understanding the rest of this page.

Mining: how the pages are sealed

Roughly every ten minutes, pending transactions are grouped into a block. To be accepted, it needs a fingerprint (a SHA-256) that starts with a required number of zeros. The only method is trial and error: miners test billions of combinations per second, and the first to find one broadcasts its block, which every node checks in a fraction of a second. In return it receives 3.125 BTC, plus the fees of the block's transactions.

Each block contains the fingerprint of the previous one. Changing an old block changes its fingerprint, which invalidates the next one, then all the others: all the mining work since that block would have to be redone, faster than the rest of the world. The energy spent is what makes the history impossible to rewrite. An Antminer S21 makes 195 trillion attempts per second; a desktop Bitaxe, 2.4 trillion, for 35 W.

Storing files on a blockchain

The same principle applies to data. Networks such as Theta, Filecoin or Arweave cut a file into fragments, copy them onto several storage nodes and write on the chain the file's fingerprint and the location of the fragments. The nodes are paid to prove regularly that they still hold their pieces. If some fail, the file is rebuilt from the others. Redundancy is calculated: with erasure coding, a fraction of the fragments is enough to rebuild the whole, where a classic host keeps several full copies.

Transparency: what blockchain brings to AI

Artificial intelligence can produce texts, images and decisions that are getting hard to tell from reality. Blockchain brings the opposite: a public, dated, tamper-proof proof. A camera can sign every image at capture time (C2PA standard) and anchor that signature on a blockchain, which attests that it came from a sensor, and when. A company can timestamp the fingerprint of a dataset and of a model's weights, and later prove what it was trained on, documentation that the AI Act requires from large models. Finally, an AI agent can pay for a service in bitcoin (Lightning) or in stablecoin, with no bank account, with a verifiable trace of every expense.

Why it matters

No intermediary: send value to anyone, at any time, without asking permission.
No single point of failure: no central server, so nothing to unplug or hack.
Verifiable by all: the code and the ledger are public, every node can recompute everything.
Uncensorable: a confirmed transaction cannot be erased by any company or any state.

Taking part at home

We sell new Bitcoin miners, tested before shipping and delivered in 7 days. To start, a Bitaxe GT 800 at 35 W tries its luck solo on a corner of a desk; an Avalon Nano 3S mines at 6 TH/s in silence; an Antminer S21 in a pool produces regular income. Our guide How to mine Bitcoin in 2026 explains the choice of machine, the setup and the profitability at your kWh price, and our calculator gives today's figures.

Frequently asked questions

Blockchain, nodes and mining: your questions

Is blockchain only Bitcoin?

No. Bitcoin is the first and the most secure, but the same principle is used to store files (Theta, Filecoin, Arweave), to run programs (Ethereum) or to timestamp documents. All rest on the same idea: a ledger copied everywhere, sealed block after block.

Why does mining consume electricity?

It is the price of security. The energy spent to seal a block is what makes rewriting it too expensive. Without that cost, anyone could rewrite the history for free. The network consumes about 175 TWh a year, in the range of Thailand; part of that energy comes from hydro surpluses or flared gas that would otherwise be lost.

What is a node, and do you have to mine to run one?

A node is a computer that keeps a copy of the ledger and checks every block. It does not necessarily mine: a Raspberry Pi with a 1 TB disk is enough to run Bitcoin Core and verify your own transactions without trusting anyone.

Can you really mine at home?

Yes. A Bitaxe or an Avalon Nano uses less than a halogen bulb and takes part in the network like any miner. The odds of finding a block alone are low, but a pool shares the rewards in proportion to the power supplied. Our guide "Solo mining or pool" details both options.

How does blockchain help AI?

It provides proof of origin. You can write into it the fingerprint of a dataset, the version of a model or the authenticity of an image, publicly and tamper-proof. It is also a native means of payment for AI agents, which have no bank account.

What happens if the majority of miners cheat?

You would need more than half of the world's power, millions of machines and billions of euros of electricity, just to cancel your own recent transactions. Even then, the nodes would reject any block that breaks the rules: cheating cannot create bitcoins or steal other people's.

Want to run a piece of the network?

We sell new Bitcoin miners, tested before shipping and delivered in 7 days, from the desktop Bitaxe to the Antminer S21, with our firmware and our after-sales service in Europe.

+33 6 32 49 26 41 Ask for advice See the Bitcoin miners

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