TL;DR: Decentralization in blockchain means distributing control, data, and decision-making across many independent participants rather than concentrating power in a single entity. It operates on three levels: architectural (how many computers form the network), political (how many organizations control those computers), and logical (whether the system behaves as one unified entity or many independent ones). Decentralization is not binary. It is a spectrum, and different blockchains make different tradeoffs along it. What matters is that decentralization enables the properties that make blockchain valuable: censorship resistance, fault tolerance, credible neutrality, and trust minimization.
The Simple Explanation
When people describe blockchain as "decentralized," they usually mean that no single company, government, or individual controls the network. But decentralization is more nuanced than that. A network can have thousands of nodes (architecturally decentralized) but be controlled by three mining pools (politically centralized). Or it can have many independent operators (politically decentralized) but rely entirely on a single cloud provider (infrastructurally concentrated).
Think of it like a voting system. A truly decentralized vote means many independent people casting ballots, many independent organizations counting them, and no single authority that can override the result. If 10,000 people vote but one company counts all the ballots, the process is architecturally distributed but politically centralized. If 100 independent counters verify the results but they all use the same counting software from one vendor, there is a logical single point of failure despite the political distribution.
Blockchain decentralization works the same way. The value comes not from the number of nodes alone but from the independence and diversity of the participants at every layer.
Three Levels of Decentralization
Architectural decentralization measures how many physical computers make up the network. A blockchain with 10,000 nodes spread across 50 countries is more architecturally decentralized than one with 100 nodes in 3 data centers. More nodes means more redundancy: the network can tolerate individual machines going offline, entire regions losing connectivity, or specific hardware configurations failing. Ethereum runs approximately 7,000-10,000 nodes globally. Bitcoin runs approximately 15,000-20,000 reachable nodes. Solana runs approximately 1,500-2,000 validators.
