What is Arbitrum?

Introduction

Arbitrum is a Layer 2 scaling solution built on top of the Ethereum blockchain. Its purpose is to make Ethereum transactions faster and dramatically cheaper without compromising Ethereum's security. While Ethereum's mainnet (Layer 1) processes every transaction itself – and is therefore slow and expensive – Arbitrum moves most of the computation off Ethereum's core network and only posts a compressed result back for verification.

You can think of Arbitrum as an Ethereum "express lane" that relieves congestion: users get the same security guarantees as Ethereum mainnet, but at a fraction of the cost and much faster. This has made Arbitrum especially popular for DeFi applications such as decentralised exchanges and lending protocols.

At the time of writing, Arbitrum is the largest Ethereum Layer 2 by total value locked (TVL), with a strong developer community and an active governance model around its ARB token. If concepts like blockchains are still new to you, start with our crypto investing basics guide.

The basics – what makes Arbitrum special?

Arbitrum is developed by US-based Offchain Labs, founded in 2018 by Ed Felten, Steven Goldfeder and Harry Kalodner. Felten previously served as the U.S. Deputy Chief Technology Officer, which has helped shape the project's regulator- and institution-friendly approach. Arbitrum One entered public beta in May 2021 and opened to general use in August 2021.

Unlike Bitcoin or Monero, Arbitrum is not an independent blockchain competing with Ethereum – it is a "child chain" built on top of Ethereum that inherits Ethereum's security and decentralisation. This also means Arbitrum has no mining or staking of its own to secure the network: security comes directly from Ethereum.

Optimistic rollups and fraud proofs

Arbitrum belongs to the optimistic rollup family. In practice, transactions on Arbitrum are assumed to be valid upfront, without an explicit proof. Transactions are batched together and their compressed data is posted to Ethereum.

If someone suspects a transaction is invalid or fraudulent, anyone can challenge it with a fraud proof during a defined challenge window. This mechanism is why moving funds from Arbitrum back to Ethereum mainnet typically takes about seven days – the time is reserved for potential disputes.

Nitro technology

Arbitrum's current technical core is the Nitro stack, deployed in August 2022, replacing the original AVM (Arbitrum Virtual Machine). Nitro is built on a modified version of Geth, the most common Ethereum node software, which makes Arbitrum's execution environment nearly identical to Ethereum.

This "Geth-at-core" architecture enables excellent EVM compatibility: developers can migrate existing Ethereum applications to Arbitrum with almost no changes. Around Nitro runs ArbOS, a lighter runtime layer that handles chain-specific tasks like fee logic, deposits, withdrawals and data compression.

BoLD – towards more decentralised validation

Arbitrum's dispute protocol is called BoLD (Bounded Liquidity Delay). It enables permissionless participation in validation: anyone can, in principle, act as a validator and challenge incorrect state claims, so validation is no longer dependent on a hand-picked set of parties. This is an important step towards a more fully decentralised Arbitrum.

One key ongoing discussion, however, is sequencer centralisation: today Offchain Labs alone is responsible for ordering transactions. A roadmap for more decentralised sequencing has been discussed in Arbitrum DAO since 2024, but the sequencer remains under Offchain Labs' control for now. Users can always force transactions directly through Ethereum if the sequencer is unavailable or censoring.

Stylus – programming with WebAssembly

Launched in 2023, Stylus expands Arbitrum's developer base by letting smart contracts be written not only in Solidity but also in languages that compile to WebAssembly (WASM), such as Rust, C and C++. This makes Arbitrum attractive for compute-intensive applications, whose performance can be significantly better than on the traditional EVM interpreter.

Use cases

Arbitrum is designed primarily as a platform where Ethereum-compatible decentralised applications can run cheaply and quickly. It is widely used in decentralised finance (DeFi) – lending and trading protocols – NFT apps, games and increasingly in tokenised real-world assets and institutional use cases.

Arbitrum also carries significant stablecoin flow: Circle's native USDC and Tether's USDT are the network's main payment rails, and Circle's CCTP protocol lets USDC move directly between chains using burn-and-mint rather than traditional bridging.

Technical view: how does Arbitrum scale Ethereum?

Arbitrum's design does not rely on trust in any single intermediary. Instead it leans on Ethereum's own security and cryptographic proof mechanisms built directly into the protocol.

Arbitrum One or Arbitrum Nova?

The Arbitrum ecosystem consists of several chains. Arbitrum One is the main network, implementing the full Rollup protocol and offering Ethereum-level security guarantees with no extra trust assumptions. Arbitrum Nova uses the lighter AnyTrust protocol, offering even lower costs and higher throughput, but relies partially on a trusted committee for data availability – best suited to applications that don't require the full decentralisation of Rollup.

Data anchoring and the fraud proof window

In practice Arbitrum's transactions are processed by the network's own sequencer, which orders and executes them quickly. The resulting data is efficiently compressed and posted in batches to the Ethereum blockchain. Once state is anchored to Ethereum, any validator can verify its correctness and, if needed, challenge it via the BoLD dispute protocol.

The seven-day challenge window is a core part of the security model: it gives independent observers time to detect and prove any misuse before funds can finally be withdrawn back to Ethereum mainnet. Billions of dollars have moved through Arbitrum without a single successful fraud attempt, which speaks to the model working in practice.

Orbit chains and "Arbitrum Everywhere"

The Nitro stack is not limited to Arbitrum One and Nova – it is also available as a modular framework anyone can use to build their own custom Layer 2 or Layer 3 chain. These are called Orbit chains, and they launched in October 2023. Several "Rollup-as-a-Service" providers such as Caldera, Gelato, Conduit and AltLayer have built businesses around deploying Orbit chains. This is part of Arbitrum's broader "Arbitrum Everywhere" vision that seeks to make Nitro a general-purpose infrastructure layer for countless applications and use cases, all governed by the Arbitrum DAO.

Technical summary

• Optimistic rollup: Transactions are assumed valid but can be challenged during the challenge window.
• Nitro / Geth core: Near-perfect EVM compatibility with Ethereum.
• BoLD: Enables permissionless, decentralised validation and dispute resolution.
• Stylus: Expands development options to WebAssembly languages like Rust.
• Orbit: Anyone can launch their own Arbitrum-based chain.

The ARB token and governance

ARB is the governance token of the Arbitrum DAO, launched in March 2023 with an initial total supply of 10 billion tokens. ARB holders vote on protocol upgrades, treasury deployments and the makeup of the Security Council. Tokens can also be delegated to another wallet if you don't want to vote actively yourself.

It's important to note that ARB does not directly collect network gas fees – all Arbitrum transaction fees are paid in ETH. ARB is therefore purely a governance token, with no automatic mechanism to direct value from network growth back to token holders unless the DAO explicitly enables such a distribution. Token supply has also faced significant unlock pressure, as team, investor and stakeholder allocations have vested in phases through 2027.

Arbitrum vs. other Ethereum Layer 2s

The Layer 2 landscape has several projects tackling the same problem: scaling Ethereum. Arbitrum's best-known competitors are Optimism, Base and the zk-rollup based zkSync and Starknet.

Optimism (OP)

Optimism is the other major optimistic rollup, using a similar fraud proof model. Optimism has built the OP Stack and the "Superchain" vision where multiple chains – including Coinbase's Base – share the same technology and security.

Difference vs. Arbitrum: Both are technically part of the same optimistic rollup family, but Arbitrum's Nitro architecture and BoLD dispute protocol have evolved on their own path, and Arbitrum has remained the single largest L2 by TVL.

Base

Base is Coinbase's L2, built on Optimism's OP Stack. Base has grown rapidly as a platform for consumer and social apps, benefitting from Coinbase's huge user base.

Difference vs. Arbitrum: Base leans more heavily on one company (Coinbase) and the OP Stack, while Arbitrum is a more independent project rooted in its own DAO and Nitro technology.

zkSync and Starknet

zkSync and Starknet represent the other rollup family: zk-rollups (zero-knowledge rollups). Instead of fraud proofs they use validity proofs, mathematically proving a batch's correctness immediately, with no challenge window.

Difference vs. Arbitrum: zk-rollups can in principle provide faster finality and, in theory, stronger security guarantees since they don't rely on an optimistic assumption. On the other hand, generating zk proofs is technically heavier, and full EVM compatibility has historically been harder to achieve than with Arbitrum's Geth-based model. Arbitrum also has a considerably longer production track record and larger existing DeFi liquidity. See our Layer 2 comparison for a broader look.

Arbitrum's strengths

• ✅ Ethereum-grade security at a low cost
• ✅ Excellent EVM compatibility thanks to Nitro
• ✅ The largest Ethereum L2 by TVL for several years running
• ✅ Expanding Orbit ecosystem for custom chains
• ✅ Active DAO and continuous development (BoLD, Stylus)

Practical guide: buying ARB and moving funds to Arbitrum

Arbitrum appeals both to developers and DeFi users who want cheap, fast execution, and to investors seeking exposure to the ARB governance token. Below is a practical overview: where to get ARB and how to move funds to the Arbitrum network safely.

Where to buy ARB

ARB is widely listed on major international crypto exchanges:

• Binance – The world's largest exchange, deep ARB liquidity
• Kraken – A trusted US-based exchange
• KuCoin – Broad crypto selection, ARB trading available
• Coinbase – Particularly relevant given the company's own strong presence in the L2 ecosystem (Base)

For beginners, a large, reputable exchange is usually the easiest starting point – ARB or ETH can then be moved to your own wallet. See our crypto investing basics guide.

Moving funds from Ethereum to Arbitrum (bridging)

Unlike an independent blockchain, using Arbitrum typically requires bridging funds from Ethereum mainnet to the Arbitrum network:

1. Connect your wallet (e.g. MetaMask) to the official bridge at bridge.arbitrum.io
2. Choose Ethereum as source and Arbitrum One as destination
3. Select the ETH or ERC-20 token to move and confirm the deposit
4. Deposits typically arrive on Arbitrum in about 10–30 minutes

Moving funds back from Arbitrum to Ethereum mainnet takes considerably longer: withdrawals through the official bridge take about seven days due to the BoLD challenge window, after which you have to separately claim the funds on the Ethereum side, which costs its own L1 gas fee. Faster alternatives include third-party "fast-fill" bridges like Across and Hop, which pre-fund the user quickly and later claim the funds themselves through the official bridge – this speed does require trusting a third party.

Storing ARB safely

Once you've acquired ARB or other assets on Arbitrum, it's recommended to move them off the exchange into your own custody. "Not your keys, not your coins" applies to Arbitrum too. Since Arbitrum is EVM-compatible, any standard Ethereum wallet works out of the box – just add the Arbitrum One network to your wallet's settings.

• Browser wallets: MetaMask (most common and widely supported), Rabby and other EVM-compatible options.
• Mobile wallets: MetaMask Mobile, Trust Wallet and Rainbow all support Arbitrum One.
• Hardware wallets: The best security for larger holdings comes from a hardware wallet. Ledger Nano X/S supports Arbitrum through MetaMask, as does Trezor Model T thanks to EVM compatibility.

Read more in our Ledger wallet security guide.

For more on wallet setup, see our how to create a crypto wallet guide.

Conclusion

Arbitrum has established itself at the heart of the Ethereum ecosystem as a solution that makes using the blockchain both cheap and fast without giving up Ethereum's security guarantees. It offers a rare combination of solid engineering and a mature, battle-tested production history, and its Nitro and BoLD technologies have proven reliable in practice over the years.

For developers Arbitrum opens the door to building Ethereum-compatible applications without mainnet's high costs, and for investors ARB provides a way to participate in the governance of one of the largest L2 ecosystems.

As with any investment or technology, do your own research and understand both the benefits and the risks – especially around ARB's supply dynamics and sequencer centralisation. In Arbitrum's case, the reward is Ethereum-level security without Ethereum-level prices: a way to use a blockchain that feels fast and cheap but ultimately rests on the same foundation of trust as Ethereum itself.