Crypto glossary
Escape hatch (forced withdrawal)
An escape hatch is a mechanism that lets users withdraw from a layer 2 directly through the base chain if its operator censors them or stops working.
Most layer 2s rely on an operator to order transactions and process withdrawals. An escape hatch is the backup path that does not need that operator's cooperation. On optimistic rollups it usually takes the form of forced inclusion: the user submits a transaction to a contract on Ethereum, and the rollup must process it within a deadline. ZK systems such as StarkEx can enter a frozen mode where users withdraw using a proof of their last balance.
Escape hatches are what make a layer 2 meaningfully non-custodial. Risk frameworks check whether one exists, how long it takes and whether upgrades could remove it before users have time to leave. Exchanges built on validity-proof systems have advertised them as proof that the team cannot lock customer funds.
Using one is slow and technical, often requiring direct contract calls rather than a wallet button, and it may cost high L1 gas. It also depends on data: in a validium, if the data holders vanish, users may not have the information needed to prove their balance, so the hatch exists only on paper.
Example
When a rollup's sequencer ignores a user's withdrawal for days, the user submits it through the L1 inbox contract and the protocol forces its inclusion after the delay expires.