Arbitrum, built by Offchain Labs and launched to Ethereum mainnet in 2021, is an optimistic-rollup layer-2 network: it executes transactions off Ethereum's main chain in batches, then posts compressed transaction data (and fraud-proof capability) back to Ethereum, inheriting Ethereum's security while offering substantially lower fees. It has grown to be one of the largest layer-2 networks by activity since launch, with its ARB governance token following in March 2023.
Category
layer-2
Consensus mechanism
Optimistic Rollup (settles to Ethereum; inherits Ethereum's security)
Launched
2021
How optimistic rollups work
Under the optimistic-rollup model, transactions are assumed valid by default (hence 'optimistic') and posted to Ethereum in batches, with a challenge window during which anyone can submit a fraud proof if they believe a batch contains invalid transactions — this is what lets Arbitrum inherit Ethereum's security rather than needing its own independent validator set and trust assumptions. This challenge-period design is also why withdrawals from Arbitrum back to Ethereum's base layer typically take longer than deposits, a trade-off common to optimistic rollups generally (versus zero-knowledge rollups, which use cryptographic proofs instead of a challenge window).
ARB token and governance
The ARB token, launched via airdrop in March 2023, is primarily a governance token for the Arbitrum DAO, which votes on protocol upgrades, treasury allocation and grants across the ecosystem (which includes Arbitrum One, the original chain, and Arbitrum Nova, a separate chain tuned for lower-cost social/gaming use cases). A significant share of ARB's total supply was allocated to team, investors and the DAO treasury on multi-year vesting schedules — check current, published unlock schedules rather than relying on launch-date figures.
Tokenomics
| circulating-supply | — |
|---|---|
| max-supply | 10,000,000,000 ARB (protocol-fixed total supply at launch) |
| issuance-model | Fixed total minted at the March 2023 token-generation event; a large share allocated to a multi-year DAO and ecosystem vesting schedule |
Last verified: 8 July 2026. before you rely on any figure — live circulating supply and market cap are never published here; check a live tracker.
Risks & criticisms
- Optimistic rollups have a challenge-period design that means withdrawals to Ethereum's base layer are slower than deposits — factor this into any time-sensitive use.
- A meaningful share of ARB's total supply is allocated to team, investors and treasury on vesting schedules — check current unlock status directly rather than relying on older figures.
- As with any layer-2, bridge contracts carry their own smart-contract risk distinct from Ethereum's base-layer security — use official, audited bridges only.
Where to buy
Related buying guide
→ Arbitrum — related buying guideFrequently asked questions
Is Arbitrum its own blockchain or part of Ethereum?
It is a separate layer-2 network that executes transactions off Ethereum's main chain and posts data back to it, inheriting Ethereum's security rather than running fully independent consensus.
What is the difference between Arbitrum One and Arbitrum Nova?
Arbitrum One is the original, general-purpose optimistic-rollup chain; Arbitrum Nova is a separate chain within the ecosystem tuned for lower-cost social and gaming applications, using a different data-availability approach.
Does ARB have a maximum supply?
Yes — 10,000,000,000 ARB was minted at the March 2023 token-generation event, a fixed total, with large portions allocated to team, investors and the DAO on multi-year vesting.