Chapter · Master Ethereum
The Merge to proof of stake
Ethereum used to secure itself with proof of work, the same energy-hungry mining that Bitcoin uses. In September 2022 it switched to proof of stake in an upgrade called the Merge. Instead of racing with power-hungry machines, the network now picks people who lock up ETH to check transactions. These people are called validators. The Merge cut Ethereum's energy use by more than ninety-nine percent while keeping the same coins and history.
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What you get asked
In what year did the Merge switch Ethereum to proof of stake?
The Merge happened in September 2022. It joined Ethereum's main chain with a proof of stake chain that had been tested in parallel.
What changed at the Merge?
The Merge replaced proof of work mining with proof of stake. Balances and history carried over unchanged. Only the way blocks get produced changed.
Under proof of stake, people who lock up ETH to help secure the network are called ___.
Validators replace miners. They put ETH at stake and are chosen to propose and check blocks, earning rewards for honest work.
Why was cutting energy use a big deal?
Proof of work needs constant heavy computation, which burns a lot of power. Proof of stake secures the chain with staked value instead, dropping energy use dramatically.
Match each idea to the right side of the Merge
Before the Merge, miners with hardware secured Ethereum. After it, validators with staked ETH do the job using far less energy.
The rest of this chapter
Learn how Ethereum works as a programmable blockchain, from smart contracts and gas to staking, Layer 2s, and DeFi.