What is Beacon Chain?
How it works
The Beacon Chain coordinates validators who must stake at least 32 ETH to participate. Validators are selected randomly to propose new blocks and attest to blocks created by others. It uses the Casper FFG finality mechanism to finalize blocks, ensuring that once a block is finalized, it is irreversible. The chain maintains a global validator set and organizes them into committees for each slot, which lasts 12 seconds.
Randomness for validator selection is generated via the RANDAO algorithm, which combines entropy from all validators' block proposals. The fork-choice rule implementing LMD GHOST ensures honest validators converge on the canonical chain. Validators are slashed for misbehavior, such as signing conflicting messages. The Beacon Chain also manages rewards and penalties, distributing ETH for honest participation and deducting for inactivity or faults.
After the Merge, the Beacon Chain became the sole consensus layer for Ethereum. The execution layer (formerly proof-of-work chain) now sends block bodies to the Beacon Chain for validation. Beacon Chain validators continue to propose and attest, but now the execution payloads include transactions from the EVM. The Beacon Chain handles finality, slashing, and protocol-level randomness for the entire Ethereum network.
Why it matters
The Beacon Chain enabled Ethereum to transition from proof-of-work to proof-of-stake, reducing energy consumption by roughly 99.95% and laying the foundation for future scalability upgrades like sharding. It introduced staking as a core Ethereum feature, allowing anyone to secure the network with ETH. Its design influenced other PoS chains and established a robust, decentralized consensus mechanism that supports restaking and liquid staking protocols.
Real-world examples
The Beacon Chain was launched on December 1, 2020, as a separate chain. Protocols like Lido and Rocket Pool built liquid staking solutions on top of it. The 'Merge' on September 15, 2022, incorporated the Beacon Chain into Ethereum mainnet. Subsequently, restaking protocols like EigenLayer emerged, using Beacon Chain validator slots as a trust base.
FAQ
What is the difference between the Beacon Chain and Ethereum mainnet before the Merge?
Before the Merge, the Beacon Chain was a separate proof-of-stake chain running in parallel with Ethereum's proof-of-work mainnet. It handled consensus only, while mainnet executed transactions. After the Merge, the two merged into a single Ethereum chain using proof-of-stake.
How does the Beacon Chain achieve finality?
The Beacon Chain uses the Casper FFG finality gadget, which finalizes blocks after two-thirds of validators attest to a checkpoint. Once finalized, a block cannot be reverted unless a supermajority of validators colludes, making Ethereum's consensus highly secure.
Can anyone run a Beacon Chain validator?
Yes, anyone can run a validator by staking at least 32 ETH and running beacon node and validator client software. Validators must remain online and follow the protocol to earn rewards; otherwise they may face penalties or slashing.
Related terms
Go deeper
Browse the complete crypto glossary to explore related terms and concepts.
Browse Glossary