First of all, I have to say the current overview page of rollups on L2beat is incredible. So much information presented in such a great way. Congratulations.

**Optimistic Rollups don’t actually work in practice** - As we know Optimistic Rollups (ORUs) are a layer-2 scaling solution for Ethereum that operate on the optimistic assumption that bundled transactions are valid. To maintain trust in this decentralized system, they use mechanisms like economic bonds and a challenge period to catch and prove faults.

However, traditional methods of proving faults can be computationally expensive - there is a reason Optimism still isn’t live with fault proofs. The only system currently in production is Arbitrum, which I wuld describe as **Interactive Fault Proof via Single Step Replay**.

**ZK Fault Proofs** - There is a new game in town that projects are calling “ZK Fault Proofs” that aim to make this verification process more efficient. By using Zero-Knowledge proofs, these methods aim to prove transaction validity or fault with a minimal computational footprint, streamlining the process while maintaining system integrity. You can check projects like: Eclipse, Fuel, LayerN, Morphism to see what its about.

### Now here is where the “ZK Rollup” term comes into being super misleading.

There are now *two different types of rollups* that use ZK tech - you could call the **pessimistic** (always prove validity) and **optimistic** (prove only when challenged) - but they both utilize zk proofs!

## This is going to create a LOT of confusion.

However, I think we can frontrun this problem as a community and come up with naming that works and actually makes sense. Does anyone have a suggestions?