Beacon Chain

The Beacon Chain is the coordination layer of Ethereum’s Proof of Stake system. Launched in December 2020, it ran in parallel with Ethereum’s original Proof of Work chain for about two years before the two merged in September 2022 in an event called the Merge. At that point, the Beacon Chain became the consensus engine of Ethereum itself — responsible for managing validators, coordinating block proposals and attestations, and maintaining the overall health and finality of the chain.

Before the Beacon Chain, Ethereum ran on Proof of Work like Bitcoin. The transition required enormous engineering work, and the Beacon Chain was the proving ground where the new validator system could be tested at scale before being trusted with the full Ethereum network. Validators staked 32 ETH to participate from day one, but for the first two years could not yet withdraw their funds — a significant commitment of trust. The Beacon Chain manages epochs and slots, assigns validators to committees, tracks balances and penalties, and implements the fork choice rules — but does not directly process user transactions, which is handled by the execution layer.

Example: Think of the Beacon Chain as the air traffic control system for Ethereum’s validators. It does not fly the planes — it does not carry the cargo (user transactions) itself. Instead, it knows where every plane is, assigns runways, manages timing, and ensures the whole operation runs in an orderly, safe way so the planes can do their jobs without colliding.