Explanation
Optimistic rollups apply a waiting period in which fraud can be proven; zk-rollups deliver an immediate mathematical proof. You mainly notice the difference on withdrawals.
Two families
Optimistic rollups assume published results are correct and give others a window to prove fraud; hence the waiting period when exiting. Zero-knowledge rollups attach a mathematical proof to each batch showing the computation was correct, making finality much faster but the technology more complex.
What it means in practice
For a user this translates into cost, speed and exit time. For institutions what matters most is whether the proof system is mature and whether the team still holds upgrade rights. Both families write their data back to the main chain, so in theory you can always reconstruct what happened yourself.
Key takeaways
- Optimistic: cheap, slow exit.
- Zero-knowledge: fast finality, more complex.
- Data remains available on layer 1.