What happens when the arbitrum sequencer goes down
The Arbitrum sequencer is not a permanent fixture. It is a single, permissioned node that orders transactions before they are finalized on Ethereum. When it stops working, users are not stuck. A fallback exists, but it is slow and requires a deliberate action.
No transaction is ever truly lost. Every user-submitted transaction is also queued into a system called the delayed inbox, which lives on Ethereum L1. The sequencer processes transactions from this inbox in batches. If the sequencer goes offline, those batches stop appearing. But the inbox keeps accepting them.
The Force-Inclusion Path
You can bypass the sequencer entirely. This is not a hidden feature. It is a core part of Arbitrum's design.
The process works through the delayed inbox contract on Ethereum. Any user can call a function on this contract to submit their transaction directly to L1. The transaction sits there, waiting. The sequencer normally pulls it and includes it in the next batch. But if the sequencer is offline, the transaction remains unprocessed for a specific period.
That period is approximately 24 hours. Once the delay expires, anyone can force the transaction through to the Arbitrum chain. This happens via a separate L1 function that literally forces the inbox to process the queued message. No permission is needed. No sequencer sign-off is required.
This mechanism is the backbone of Arbitrum's censorship resistance. It guarantees that the sequencer, even if malicious or broken, cannot permanently prevent a user from moving their funds or executing a contract. The price is time: a full day of waiting.
How to do it
The steps are straightforward. You need an Ethereum wallet and a small amount of ETH for L1 gas.
First, send your transaction to the delayed inbox address on L1. This is a standard Ethereum transaction. The exact contract address varies by chain - Arbitrum One uses a different inbox than Nova - and you can find it in the official Arbitrum documentation. The transaction must include the exact calldata you want executed on the Arbitrum chain.
Wait roughly 24 hours. There is no shortcut; the delay is fixed.
After the delay, call the forceInclusion function on the sequencer inbox contract. This function checks that the delayed inbox message has aged enough, then processes it. The transaction is now executed on Arbitrum as if the sequencer had handled it normally.
You will pay L1 gas fees both times - once to submit to the delayed inbox, once to force inclusion. The total cost is higher than a normal Arbitrum transaction. But the alternative, being stuck, is often worse.
Why nova is different
The above path works on Arbitrum One. It does not work on Arbitrum Nova.
Nova uses a different data availability model called AnyTrust. Instead of posting all transaction data to Ethereum L1, it relies on a Data Availability Committee (DAC) of trusted validators. The DAC attests that they hold the data. This reduces L1 costs dramatically. It also removes the delayed inbox as a meaningful escape hatch.
There is no force-inclusion mechanism on Nova that mirrors Arbitrum One's. The AnyTrust design means the sequencer's liveness is more tightly coupled to the DAC's cooperation. If the sequencer stops working on Nova, users cannot simply wait a day and force their transactions through. The data needed to reconstruct the chain state may not be available on L1.
This is a trade-off. Nova is cheaper, faster, and designed for high-frequency applications like gaming, but it sacrifices the full censorship resistance that Arbitrum One retains. For users who demand the ability to exit or transact regardless of the sequencer, Arbitrum One is the safer choice.
What this means in practice
Sequencer downtime is rare but not unheard of. Arbitrum's sequencer has experienced outages before, typically lasting a few hours. During those windows, the delayed inbox continued accepting submissions. No funds were lost. The chain reorganized and continued once the sequencer resumed.
The real risk is not a temporary outage. It is a permanent sequencer failure or a deliberate censorship attempt. In that scenario, the delayed inbox path is your exit. It exists, it works, and it requires no trust in any third party.
But you must know it exists. If you are using Arbitrum One today, you have this safety net. The 24-hour delay is the cost of that guarantee. For Nova users, the safety net is absent. That is by design.
Before you choose which chain to use, understand what you are giving up. Arbitrum One offers a proven, if slow, escape route. Nova does not. Neither is wrong. But the difference matters when the sequencer stops.
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