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These FAQs are targeted toward devs and researchers who already have some familiarity with Arbitrum; if you're new here, you may want to start with our gentle introduction (Also, welcome!)


How does gas work on Arbitrum chains?

Why does it look like two identical transactions consume a different amount of gas?

How is the L1 portion of an Arbitrum transaction’s gas fee computed?

Does Arbitrum have a mempool?

Do I need to pay a Priority fee for my Arbitrum transactions?

Running Nodes

How do I run a nitro node locally for development?

Can I run an Arbitrum Node in p2p mode?

Cross Chain Messaging

How can I check the status of my cross chain message?

When I initiate withdrawal from Arbitrum, how long does it take before I receive my funds?

What is a retryable ticket’s “submission fee”? How can I calculate it? What happens if the fee I provide is insufficient?

Which method in the Inbox contract should I use to submit a retryable ticket?


What's the difference between Arbitrum Rollup and Arbitrum AnyTrust?

Are “Sequencers” the same thing as “Validators”? Can a centralized Sequencer do bad things like stealing all my money?

If there is a dispute, can my L2 transaction get reorged / thrown out / "yeeted"?

...okay but if there's a dispute, will my transaction get delayed?

Why was “one week” chosen for Arbitrum One’s dispute window?

Dev Tooling

Do I need to download any special npm libraries in order to use web3.js or ethers-js on Arbitrum?

Why do I get “custom tx type” errors when I use hardhat?


How do block.timestamp and block.number work on Arbitrum?

What’s the state of Arbitrum One’s decentralization?