A record book no one can secretly change.
Imagine a shared spreadsheet of who owns what. Instead of one bank keeping it, thousands of computers each hold an identical copy. To add a new line, most of them have to agree it's valid, and once it's written, it can't be quietly edited. That shared, agreed, permanent record is a blockchain.
It's a ledger
A running list of every transaction, grouped into blocks. New blocks link to the last one, forming a chain back to the very first.
It's shared
Copies live on computers (nodes) all over the world. No single company owns it or can switch it off, it's decentralized.
It's secure
Maths (cryptography) and group agreement (consensus) make records practically impossible to fake or reverse.
It's open
Anyone, anywhere can check it or use it, no application, no permission, no opening hours. It runs 24/7.
From “send” to settled, step by step.
When you send crypto, no bank approves it. Instead the network checks and records it together. Here's the journey of a single transaction.
When a new block is added, every node updates its copy. To cheat, you'd have to fool a majority of them at once, across the whole world, all at the same time.
“Consensus” is just the rule for deciding who gets to add the next block, and it's what keeps the whole thing honest without a boss. Two main approaches power most chains:
Computers race to solve a hard puzzle, spending electricity. The winner adds the block.
- Battle-tested security
- Energy-intensive by design
Validators lock up coins as a bond and take turns. Cheating costs them their stake.
- ~99% less energy
- Earn rewards by staking
Each block carries a fingerprint (a hash) of its contents, and every block includes the one before it. Change anything, even one character, and its fingerprint changes, breaking every block after it. Edit a block below and watch the chain break.
The chain is valid. Every block's fingerprint matches the next. Try editing any block's data.
Not all chains are the same.
Chains differ in two big ways: which layer they sit at, and what they're built for. Understanding both makes it easy to tell why Bitcoin, Ethereum, Solana and Arbitrum feel so different.
The foundation
A Layer 1 secures itself and settles its own transactions, the bedrock everything else builds on. Bitcoin, Ethereum and Solana are all L1s, each with its own security and rules.
The fast lane
A Layer 2 runs on top of an L1 to make it faster and cheaper, then posts results back down for security. Arbitrum, Optimism and Base are L2s that settle to Ethereum.
Digital money
Built first and foremost to store and move value, scarce, secure, simple. The “digital gold” category.
Explore BitcoinSmart-contract platforms
General-purpose chains that run programs, the home of DeFi, stablecoins, NFTs and most tokens.
Explore EthereumHigh-performance L1s
Chains tuned for raw speed and low fees, built for consumer-scale apps, payments and trading.
Explore SolanaLayer 2 rollups
Scale an existing L1 to cent-level fees while inheriting its security, most everyday Ethereum activity lives here.
Explore ArbitrumHow a network agrees, without a boss.
“Consensus” is the rulebook for who gets to add the next block and how everyone agrees it's valid. It's the heart of what makes a blockchain trustworthy. Here are the main approaches, and the chains that use them.
Computers race to solve a hard puzzle, spending real electricity. The winner adds the block, rewriting history would cost a fortune.
Validators lock up coins as a bond and take turns adding blocks. Honest work earns rewards; cheating burns the stake.
A cryptographic “clock” timestamps events before consensus, so validators don't waste time agreeing on order, enabling huge speed.
What this unlocks.
Removing the middleman isn't just a technical trick, it changes who's in control. Here's why people build on and use blockchains.
You own it
With a self-custodial wallet, your coins are yours, no bank can freeze, block or seize them. Your keys, your crypto.
Borderless & instant
Send value across borders in minutes, or seconds, without intermediaries or waiting for business hours.
Transparent
Anyone can audit the ledger and verify the rules. Trust comes from open code and maths, not a promise.
Programmable
Smart contracts let money follow rules automatically, powering lending, savings, payments and apps with no bank.
Open to everyone
All you need is a phone. No credit check, no bank account, a path to finance for billions who lack one.
Sound money
Many chains have fixed or predictable supply written in code, no one can print more on a whim.
The words you'll keep hearing.
A quick, plain-English glossary of the terms that show up everywhere in crypto. Tap any card for the full definition, or browse the complete crypto glossary.
A wallet holds your private key, a secret that proves ownership and signs transactions. Lose it and you lose access; share it and others can spend. Self-custody means only you hold it.
In the glossaryA coin is a chain's native asset (BTC, ETH, SOL). A token is built on top of a chain using a standard (like ERC-20), stablecoins and most others are tokens.
In the glossaryA small fee paid to the network to process your transaction. It rewards validators and prevents spam. Busy chains cost more; fast chains and L2s cost cents.
In the glossarySelf-running code stored on a chain that executes exactly as written when conditions are met, no middleman. The engine behind DeFi, NFTs and most apps.
In the glossaryA Layer 1 is a base chain (Ethereum, Bitcoin). A Layer 2 runs on top to make it faster and cheaper, settling back to the L1 for security.
In the glossary“Decentralized finance”, lending, trading, saving and earning yield through smart contracts instead of banks. Open to anyone with a wallet.
In the glossaryNow meet the blockchains.
Every chain makes different trade-offs between speed, cost, security and what you can build. Dive into any one for a plain-English profile of how it works and what it's used for.
Still wondering?
Is blockchain the same as cryptocurrency?
Who controls a blockchain?
Er det sikkert?
Why are there so many blockchains?
How do I actually use one?
Resources & further reading.
From learning to doing.
Hold, swap and spend crypto across 20+ blockchains in one self-custodial app, with a real Visa card for the real world.
Self-custodial · non-custodial · your keys, your coins.Udforsk kryptotrends
