Arbitrum One (chain ID 42161) and Nova (chain ID 42170) — the highest-TVL EVM L2 ecosystem, powered by Nitro (WASM-based fraud proofs) and Stylus (Rust/C++/C smart contracts on the same chain as Solidity). Default L2 for serious DeFi, derivatives (GMX, Camelot, Hyperliquid bridge), and any product that needs deep onchain liquidity with sub-cent fees.
- 01high-TVL DeFi and derivatives
- 02Stylus contracts (Rust/C++/C running alongside EVM)
- 03Orbit chains — sovereign Arbitrum-stack L2s/L3s
- 04low-fee NFT and gaming on Nova (DAC-based)
- 05BoLD-enabled permissionless fraud proofs
- pnpm add viem wagmi
- # Stylus toolchain (optional, for Rust/C++ contracts):
- cargo install --force cargo-stylus
| Variable | Scope | Description |
|---|---|---|
| NEXT_PUBLIC_ARB_RPC_URL | Client | Arbitrum One RPC URL. Public is `https://arb1.arbitrum.io/rpc` (rate-limited) — use Alchemy/QuickNode/Offchain Labs for production. |
| NEXT_PUBLIC_ARB_CHAIN_ID | Client | Chain ID — 42161 for Arbitrum One, 42170 for Nova, 421614 for Sepolia rollup testnet. |
Use viem's built-in `arbitrum` / `arbitrumNova` / `arbitrumSepolia` chains. Reads and writes are standard EVM via wagmi/viem. For Stylus contracts, scaffold with `cargo stylus new my-contract`, deploy with `cargo stylus deploy --private-key-path ...`, then call them from Solidity or directly from viem — they share an address space with EVM contracts. For Orbit (Arbitrum-stack L2/L3) deployment, use the Orbit SDK at `@arbitrum/orbit-sdk`. Cross-chain ETH/token transfers use the Arbitrum Bridge contracts (`L1GatewayRouter`/`L2GatewayRouter`); for instant withdrawals use Across, Stargate, or Hop.
- ⚑L2→L1 withdrawals have a 7-day challenge period — use a fast-bridge (Across, Stargate, Hop) for user-facing exits, never the native bridge.
- ⚑Arbitrum One uses BoLD for permissionless fraud proofs (live since 2025); challenge windows are now ~6.4 days. Verify your bridge integrations have updated to the current dispute timing.
- ⚑Nova is a DAC (Data Availability Committee) chain — cheaper but with weaker DA guarantees than One. Don't put high-value DeFi on Nova; it's optimized for gaming/social.
- ⚑Stylus contracts share state and addresses with Solidity contracts but have different gas dynamics — Rust ops are 10-100× cheaper than EVM equivalents for compute-heavy code.
- ⚑`tx.origin` and block timestamps behave subtly differently from L1 — re-test any contract that relies on them after porting.
- ⚑Arbitrum Stylus is opt-in per chain — verify the target Orbit chain has Stylus enabled before deploying Rust contracts to it.