Arbitrum

Arbitrum is a set of networks that process transactions off Ethereum and post the results back to it, so users pay less gas while Ethereum stays the place where disputes are settled. There are two production chains. Arbitrum One is an optimistic rollup that posts all of its transaction data to Ethereum. Arbitrum Nova uses the AnyTrust design, where a data availability committee holds the data and Ethereum is used only if the committee fails.

No single company owns the networks in the usual sense. The ArbitrumDAO, whose members vote with the ARB token, controls the chains' contracts and treasury through the process set out in its constitution. The Arbitrum Foundation, a Cayman Islands foundation company, acts as the DAO's steward: it funds development and grants, contracts service providers, oversees the DAO-approved chains and runs the sequencer. The DAO can elect or remove the Foundation's directors.

The core software, including the Nitro node, the SDK and the bridge tutorials, is published under the Offchain Labs organization on GitHub, which the Arbitrum docs link to. Offchain Labs is the company most associated with building Arbitrum; Offchain, Inc. is also listed as one of Nova's committee members.

ARB is a governance token. It is minted on Arbitrum One and lets holders vote on Arbitrum Improvement Proposals or delegate their votes. Gas on both chains is paid in ETH, not ARB. CoinGecko shows a total supply of 10 billion ARB and about 6.89 billion in circulation as of October 2026.

The Arbitrum bridge is the canonical route between Ethereum and Arbitrum: a set of contracts on both chains, plus the web interface at portal.arbitrum.io/bridge. It does not rely on an outside group of signers to confirm transfers. A deposit is a message from Ethereum to Arbitrum; a withdrawal is a message from Arbitrum to Ethereum that only becomes final after the rollup's dispute window.

Deposits go through Ethereum's Inbox contract as so-called retryable tickets. ERC-20 tokens move through gateway contracts: most tokens use the standard gateway, which creates a matching token on Arbitrum automatically, while some issuers use a custom gateway. Arbitrum's docs say a deposit is processed on the child chain typically within a few minutes.

Withdrawals work the other way. Your tokens are burned or locked on Arbitrum, and a message waits in an Outbox until the state that contains it has been confirmed on Ethereum. On Arbitrum One that dispute window is 45,818 Ethereum blocks, about 6.4 days, and the keyword phrase "7 days" is a rounding of this. After it passes you, or anyone, sends one more transaction on Ethereum to claim the funds.

The canonical bridge connects Ethereum with Arbitrum chains only. Searches such as "Solana to Arbitrum", "BSC to Arbitrum" or "Polygon to Arbitrum" describe routes it does not serve; those need a third-party bridge or an exchange that supports both networks. Bridge aggregators also route through it: LI.FI's live tool list includes "Arbitrum Bridge" as one of its options. If you want a faster exit than 6.4 days, third-party bridges such as Across pay you out early and take the settlement wait on themselves, for a fee and with their own contract risk.

The Arbitrum docs do not describe a separate bridge fee. What you pay is gas. A deposit costs Ethereum gas for the deposit transaction plus a small amount that pays for the retryable ticket and its execution on Arbitrum, which the SDK and the portal calculate for you. A withdrawal costs Arbitrum gas to start and Ethereum gas for the final claim, and the claim is usually the larger cost because it runs on Ethereum.

On Arbitrum One the gas price floor is 0.02 gwei and there is no need for a priority fee, because the sequencer orders transactions first come, first served and refunds any tip. Ethereum gas varies by the minute, so the cost of a deposit or a claim depends on when you send it. Third-party bridges and aggregators add their own fees on top of gas; the canonical route does not.

The bridge's security comes from the rollup's proof system, not from a committee of signers. On Arbitrum One, validation runs on the BoLD dispute protocol and is permissionless: the Foundation's own decentralization page says any node that implements BoLD can join. Anyone proposing a new state must post a bond of 3,600 ETH, and anyone who disagrees can challenge it during the dispute window. That window is why withdrawals take about 6.4 days.

Three trust points remain, and the Foundation lists them itself. First, the sequencer is run by the Arbitrum Foundation. It can delay a transaction by up to 24 hours or reorder transactions over short periods, but it cannot steal funds, and after 24 hours a user can force a transaction in through Ethereum. Second, the Security Council, a 9-of-12 multisig elected by the DAO in two cohorts, holds chain-owner powers and can act quickly in a critical emergency, including upgrading contracts. Third, Nova depends on a 5-of-6 data availability committee whose members are ConsenSys Software Inc., QuickNode, P2P.org, Google Cloud, Offchain, Inc. and Opensea Innovation Labs.

Ordinary upgrades go through the DAO. Under the constitution, a passed proposal that changes Ethereum-side contracts waits 8 days on Arbitrum, then at least one rollup challenge period, then 3 more days on Ethereum before it takes effect. The stated purpose is to give users who object time to withdraw.

The Arbitrum docs list security reviews by Trail of Bits and OpenZeppelin, the most recent dated 19 October 2026, and DefiLlama links a Quantstamp audit of the token bridge. An audit is a review at a point in time, not a guarantee. The Immunefi bug bounty pays up to $2 million and has been live since 31 August 2021. We found no record of an exploit of the canonical bridge contracts in the sources we checked. For a comparison with third-party bridges, see how the canonical route compares with other bridges.

To bridge ETH from Ethereum to Arbitrum, open portal.arbitrum.io/bridge, connect a self-custody wallet such as MetaMask, choose Ethereum as the source and Arbitrum One as the destination, and confirm. Keep some ETH on Arbitrum for gas, because every later transaction there is paid in ETH. Check the exact URL before connecting: searches for "official Arbitrum bridge" are a common target for look-alike sites.

To leave, start the withdrawal on the same page. The portal shows a countdown, and after about 6.4 days the withdrawal becomes claimable in the transaction history tab, where you sign the claim on Ethereum. Funds are not credited until you claim. If you sent from another interface or lost track of a transfer, paste the transaction hash into the portal's history or its Retryable Tickets tool.

Two mistakes cannot be undone by the bridge. Sending tokens over Arbitrum to an exchange account that does not support Arbitrum may lose them; the FAQ says only the exchange can help. And some tokens exist in more than one version on Arbitrum. USDC, for example, appears as both USDC and USDC.e in bridge token lists, so check which one your wallet or exchange expects before you move it.

Arbitrum's support desk takes requests through a form at support.arbitrum.io, and the community runs on Discord (discord.gg/arbitrum) and X (@arbitrum). Network status, including the sequencer, batch poster and validators for Arbitrum One and Nova, is published at status.arbitrum.io, which showed full uptime for August to October 2026.

No support agent will ask for a seed phrase or send a link to "fix" a withdrawal. A stuck deposit or withdrawal can be checked and finished by the user from the portal's transaction history with the original transaction hash, so a message offering to recover funds for you is a scam.

The Arbitrum bug bounty on Immunefi went live on 31 August 2021. Governance moved to the ArbitrumDAO with the ARB token, and the Foundation's bylaws in its public documents are dated July 2023. The older Classic technology was replaced by Nitro, which runs both production chains today.

Test networks have come and gone: Arbitrum Goerli was deprecated on 18 November 2023 and switched off on 18 March 2024, and the standalone Stylus testnet closed on 17 June 2024 once Stylus reached Arbitrum One. In August 2026 the DAO voted to extend Security Council terms to two years, starting with the March 2026 cohort. Audit work continues at a steady pace, with Trail of Bits reviews of ArbOS 60 and 61 in July 2026 and of gas parameters for Ethereum's Glamsterdam upgrade in October 2026.