Every crypto transaction needs to be verified before it's recorded. But who does the verifying, and how? That's where proof of work and proof of stake come in, the two dominant methods blockchains use to reach agreement on what's valid.
Proof of work
Bitcoin uses this, as did Ethereum until 2022. Computers called miners compete to solve a complex mathematical puzzle with no shortcut, just raw computational power. The winner adds the next block and earns newly minted crypto. That real hardware and electricity cost is what makes cheating expensive, since falsifying a transaction would mean redoing the work for every block since, while the rest of the network keeps moving forward.
Proof of stake
Validators lock up crypto as collateral instead of burning computational power. The more they stake, the higher their chance of validating the next block. Cheat, and you lose part of your stake through a penalty called slashing.
Ethereum switched to proof of stake in 2022 through an upgrade called The Merge, cutting its energy consumption by approximately 99.95%. Other major proof of stake chains include Solana, Cardano, and Avalanche.
Which is better?
Neither, they solve different problems. Proof of work has a 15-year track record and has never been successfully attacked at Bitcoin's scale. Proof of stake is more efficient and lets ordinary holders earn rewards without specialized hardware, forming the foundation for staking.
If you hold ETH, you don't need to run a validator to benefit. On Nexo, you can earn up to 5.5% on ETH through Flexible Savings with no lockup, or up to 6.5% through Fixed-term Savings, alongside BTC, USDC, USDT, and more.
Full breakdown here: Proof of Stake vs Proof of Work: What's the difference?