When the sequencer does not respond
Most layer 2 rollups rely on a sequencer, an operator that accepts users' transactions, orders them, and produces blocks. The sequencer makes transactions fast and cheap, but if it stops or refuses certain transactions, users may seem unable to do anything on the rollup.
To guard against this, some rollups provide a forced inclusion path: users submit a transaction directly on Ethereum, and after a set time it must be included in the rollup even without the sequencer. Here we cover how that path works, how long it actually takes, and how long a withdrawal takes end to end, using a hypothetical case and official documentation.
The sequencer's role and limits
As Ethereum.org's page on optimistic rollups explains, the sequencer collects and orders transactions and posts the results to Ethereum in batches. Many rollups today run a single sequencer operated by one company. In that setup the sequencer cannot steal funds, but it can delay or refuse transactions.
Censorship resistance is the property that users can eventually get their transactions processed anyway. A forced inclusion path is the last line of defense: users bypass the sequencer and put a transaction directly into the rollup's contract on Ethereum.
Forced inclusion as documented
The OP Stack documentation explains that users can submit L2 transactions as deposit transactions through a contract on Ethereum, and that a 12-hour sequencing window bounds when transactions must be included. With a healthy sequencer, deposit transactions are included within at most 30 minutes.
Arbitrum's documentation explains that users can place transactions in the delayed inbox on Ethereum, and if the sequencer does not process them within 24 hours, anyone can include them using the forceInclusion function. In both cases the user pays Ethereum gas directly.
| Design | Where to submit | Wait if the sequencer ignores it | User cost | Watch out for |
|---|---|---|---|---|
| OP Stack | Portal contract on Ethereum (deposit transaction) | Up to the 12-hour sequencing window | Ethereum gas | Tooling and transaction format |
| Arbitrum | Delayed inbox on Ethereum | forceInclusion possible after 24 hours | Ethereum gas | A direct call is needed after 24 hours |
| Rollup with no forced path | None | Until the operator resumes | — | Complete dependence on the operator |
Figures summarize each project's documentation and may change with network upgrades.
A hypothetical withdrawal
Suppose a user on an Arbitrum-style rollup wants to start a withdrawal, but the sequencer keeps ignoring the transaction. The user places the withdrawal transaction in the delayed inbox on Ethereum, waits 24 hours, and then calls forceInclusion. Only then does the withdrawal start on the rollup.
An optimistic rollup withdrawal then goes through a challenge period of about seven days before funds can be claimed on Ethereum. The user's funds become usable on Ethereum after roughly one day plus seven, about eight days, plus inclusion delays and Ethereum gas. Forced inclusion protects funds; it does not get them out quickly.
Why a path can still be hard to use
Forced inclusion is usually not a button in an ordinary wallet. It requires submitting correctly formatted data to an Ethereum contract, often by following official tools or developer documentation. Attempting it for the first time amid the confusion of a sequencer outage invites mistakes.
When Ethereum is congested, gas can spike, and for small balances the cost of forced inclusion may exceed their value. That a path exists and that it can actually be used are different questions.
Practicing once with a tiny amount while everything is working normally is the best preparation. The steps, the tools, and the costs are much easier to learn without the pressure of an outage.
What to check in advance
Before keeping funds on a rollup, work through these items.
- Find whether the rollup's official documentation describes a forced inclusion or censorship-resistance path.
- Check how long you must wait if the sequencer ignores your transaction and what you must do afterward.
- See whether official tools or step-by-step guides exist for forced inclusion.
- Add the forced inclusion wait to the withdrawal challenge period to estimate the worst-case time to get funds out.
- Judge whether the cost of forced inclusion at high Ethereum gas prices is reasonable relative to your balance.
Read it alongside upgrade powers
Even with a forced inclusion path, if an admin can upgrade the rollup's Ethereum contracts immediately, the path could be removed. Check whether contract upgrades are delayed and whether the delay is longer than the time needed for forced inclusion and withdrawal.
Decentralized sequencing, with several parties sharing the sequencer role, is also under discussion. Arbitrum's documentation notes that decentralized sequencing changes who enforces the ordering rules, not the rules themselves. Whatever the structure, it remains worth checking what the last line of defense is.
Applying it in practice
The waits here summarize official documentation, and the withdrawal case is hypothetical. Real rollups may differ by version and configuration, and upgrades can change the procedures.
When checking, use Ethereum.org and each rollup's current documentation with their revision dates in mind. Treat the numbers as material for your own judgment, not as trading signals.