ZK vs. Optimistic roll ups

Layer 2 (L2) blockchains come in two forms: Zero Knowledge (ZK) and Optimistic roll ups.

Layer 2 (L2) blockchains build on top of core blockchains like Ethereum to reduce costs and increase speed. The two most common L2s are ZK roll ups and optimistic rollups. Understanding their nuances will help you make the right choice.

Roll ups: buy wholesale to reduce costs

Roll ups package transactions and process them off-chain.

ZK and Optimistic roll ups are the mechanisms used by L2's to prove their validity to the L1 (e.g. Ethereum).

Optimistic: innocent until proven guilty

Assumes validity, but anyone is free to challenge them.

Optimistic roll ups submit their transactions without proof. Other nodes in the network can challenge a transaction if they believe it’s inaccurate. If their challenge holds, they are rewarded for it.

ZK: submit your evidence

Submit transactions with proofs to the L1.

They run the code they need to process, construct a cryptographic proof and submit the result to the L1. The key takeaway is that a ZK roll up may require a significant amount of computing power.

Which one is better?

Optimistic roll ups are EVM compatible and use less computing power. But it can take time for a transaction to be verified (due to the challenge). ZK roll ups are guaranteed to be verified as they are submitted with proof. They use more computing power, and are not always EVM compatible. If you have less computing to do on-chain, it may be more economical to go with Optimistic roll ups.