All terms
A rollup that assumes transactions are valid unless someone proves otherwise.
Optimistic rollups post results and open a challenge window, typically seven days. Anyone can submit a fraud proof during that period to reverse an invalid batch.
The tradeoff is withdrawal time. Moving funds back to layer 1 through the official route means waiting out that window, though bridges offer instant exits for a fee.
Arbitrum, Base, OP Mainnet and Blast are all optimistic rollups.
That the challenge period is a formality. It is the security model. During that window a fraudulent state can still be disputed, which is exactly why withdrawing to the base chain takes days rather than minutes.
Common questions
What does the challenge period protect against?
Has anyone ever actually submitted a fraud proof?
Where this comes up on the site
The guides that actually use this word, rather than a list of everything we have written.
Where to go next
More technology terms
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