Optimistic Rollups
scaling solution
Optimistic Rollups are Layer 2 scaling solutions that bundle multiple transactions off-chain and post them to the main blockchain under the assumption that all are valid ÔÇö hence the name ÔÇ£optimistic.ÔÇØ Unlike ZK-Rollups, they donÔÇÖt require cryptographic proofs upfront. Instead, they rely on fraud proofs: if someone challenges an invalid transaction during the dispute window, the system can revert it. This method reduces fees and congestion while maintaining Ethereum security and EVM compatibility, but trades off immediate finality.
Use Case: Optimistic Rollups enable cheaper, scalable dApp execution on Ethereum-compatible chains without needing cryptographic infrastructure at the point of transaction.
Key Concepts:
- Fraud Proof ÔÇö A challenge system used to dispute invalid rollup data
- Dispute Window ÔÇö A period (e.g., 7 days) where transactions can be contested
- Layer 2 Scaling ÔÇö Off-chain processing to reduce mainnet load
- EVM Compatibility ÔÇö Seamless use of Ethereum-based tools and dApps
Summary: Optimistic Rollups prioritize compatibility and scalability by deferring validation. They are easier to implement than ZK-Rollups and widely adopted, though users must wait for the challenge period to confirm finality.
| Feature | ZK-Rollups | Optimistic Rollups |
|---|---|---|
| Validation | Cryptographic validity proofs | Assumes validity; uses fraud proofs if challenged |
| Finality Speed | Near-instant (no dispute period) | Slower (dispute window typically ~7 days) |
| Security Model | Mathematical proof of correctness | Relies on honest participants to flag fraud |
| EVM Compatibility | More complex; evolving EVM support | High compatibility with Ethereum apps |
| Examples | zkSync, StarkNet, Polygon zkEVM | Optimism, Arbitrum, Base |