What is a Blockchain?
A blockchain is a shared, immutable digital ledger that records transactions across a network of computers. Think of it as a public notebook that everyone can read, but no single person can erase or change what's already been written.
How Does It Work?
- Transactions are broadcast to the network when someone sends cryptocurrency, interacts with a smart contract, or performs any on-chain action.
- Blocks are created by miners or validators who bundle pending transactions together. Each block contains a list of transactions, a timestamp, and a reference to the previous block.
- The Chain is formed because each block points to the one before it, creating an unbreakable sequence. If someone tried to alter a past block, it would break the chain from that point forward.
- Consensus ensures everyone agrees on the current state. Different blockchains use different methods (Proof of Work, Proof of Stake, etc.) but the goal is the same: agreement without a central authority.
Key Properties
- Decentralized: No single company or government controls it. The network is run by thousands of independent computers (nodes) worldwide.
- Immutable: Once data is written to the blockchain, it cannot be changed or deleted. This creates a permanent, auditable record.
- Transparent: Anyone can view the data on a public blockchain using a block explorer like Omniscanner.
- Trustless: You don't need to trust a middleman. The math and code handle verification.
Types of Blockchains
| Type | Examples | Key Feature |
|---|---|---|
| Layer 1 | Ethereum, Bitcoin, Solana | The main chain that processes transactions directly |
| Layer 2 | Arbitrum, Base, Optimism | Built on top of L1s for faster, cheaper transactions |
| Sidechains | Polygon, Gnosis | Independent chains connected to a main chain |
| Appchains | dYdX, Osmosis | Chains built for a specific application |
Why Does It Matter?
Blockchains enable trustless systems where value can be transferred without intermediaries. This has applications in finance (DeFi), digital ownership (NFTs), supply chain tracking, identity verification, and more.
You can explore real blockchain data right now using Omniscanner -- just pick a network from the dropdown and start browsing blocks and transactions.