🤝Basics

What is Consensus? How Blockchains Agree

January 20, 2025
5 min read

Imagine you and your friends want to decide where to eat. Everyone needs to agree on one place. That's basically what consensus means — everyone agreeing on the same thing!

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Simple Definition: Consensus is when all computers in a blockchain network agree on what information is correct and should be added to the blockchain.

🤔 Why Do We Need Consensus?

In a regular bank, there's one central computer that keeps track of everyone's money. Easy, right? But what if that computer makes a mistake or someone hacks it?

Blockchain is different. Instead of one computer, there are thousands of computers around the world, all keeping the same record. But here's the tricky part:

The Problem: How do thousands of computers agree on what's true when they can't see or trust each other?

That's where consensus comes in! It's like having rules for a game so everyone plays fairly.

🎮 A Simple Example

Let's say Alice wants to send 10 coins to Bob:

1
Alice announces: "I'm sending 10 coins to Bob!"
2
All computers check: "Does Alice really have 10 coins?"
3
Computers agree: "Yes, Alice has enough. This transaction is valid!"
4
Transaction recorded: Everyone updates their records at the same time.

🔧 Types of Consensus

There are different ways computers can agree. The two most popular are:

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Proof of Work

Computers solve hard puzzles to earn the right to add new information. Like winning a math competition!

Used by Bitcoin
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Proof of Stake

People who own more coins get to help verify transactions. Like voting based on how much you've invested!

Used by Ethereum

✨ Why Consensus Matters

🔒 Security

No single person can cheat the system

🌍 Decentralization

No one company controls everything

Trust

You can trust the system without trusting individuals

📖 Transparency

Everyone can see and verify the same information

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Key Takeaway: Consensus is like the referee of blockchain — it makes sure everyone follows the rules and agrees on what's true, even when they don't know each other!