🔀 When Blockchains Split: Understanding Forks
Learn what happens when two miners find blocks at the same time
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0 / 5 completed🔀 Blockchain Forks & Reorganization
What happens when two miners create blocks at the same time? Or when the blockchain protocol needs to upgrade? Welcome to the world of forks and chain reorganizations!
🎯 What is a Fork?
A fork occurs when the blockchain splits into two or more competing chains. Think of it like a road diverging - suddenly there are multiple valid paths forward.
🎮 Interactive Fork Type Explorer
Click each fork type to understand what causes it:
Temporary Fork
Two miners find blocks simultaneously, creating competing chains that resolve quickly
⚡ Why Forks Happen
Two miners find valid blocks at nearly the same time. The network hasn't fully synchronized, creating temporary competing chains.
Developers introduce new rules or features. Nodes must upgrade software to follow new consensus rules.
Major disputes about blockchain direction can cause permanent splits (like Ethereum/Ethereum Classic).
Software bugs or malicious attacks can cause unexpected forks that require emergency coordination.
🔍 The Longest Chain Rule
Bitcoin and most Proof-of-Work blockchains follow a simple principle: the longest valid chain wins.
Two valid blocks found at height 1000, creating Chain A and Chain B
Some work on Chain A, others on Chain B. Next blocks (1001) built on each
Chain A finds block 1002 first. It's now longer (1002 vs 1001)
All nodes switch to Chain A. Chain B becomes orphaned history
Actually it's the chain with the most accumulated work (difficulty). "Longest" is shorthand - it's really "most computational effort invested."
📊 Real-World Fork Examples
Type: Hard fork | Reason: Debate over block size limits. Created permanent split between BTC and BCH.
Type: Hard fork | Reason: Response to DAO hack. Split into ETH (rolled back) and ETC (immutable chain).
Type: Soft fork | Reason: Bitcoin scaling improvement. Backward compatible - old nodes still worked.