# Arbitrum

> Arbitrum One and Arbitrum Sepolia through RPC Gateway, with chain IDs, provider coverage, and the calls served without an Endpoint.

Canonical page: https://rpc.aurpay.net/docs/chains/arbitrum

Arbitrum is an EVM rollup in the Gateway catalog. Its gas token is ETH, and any standard EVM client can talk to the Gateway Access Point without special configuration.

## Networks and hosts

| Network | Chain ID | JSON-RPC Host |
|---|---:|---|
| Mainnet | 42161 | `arb-jsonrpc` |
| Sepolia | 421614 | `arb-sepolia-jsonrpc` |

Chain ID 42161 is Arbitrum One and 421614 is Arbitrum Sepolia; other Arbitrum chains are outside the current [supported networks](https://rpc.aurpay.net/docs/supported-networks.md) table. Copy the complete Access Point from the dashboard.

## Provider coverage

| Provider | Mainnet | Sepolia |
|---|:---:|:---:|
| [Alchemy](https://rpc.aurpay.net/docs/providers/alchemy.md) | Yes | Yes |
| [QuickNode](https://rpc.aurpay.net/docs/providers/quicknode.md) | Yes | Yes |
| [Chainstack](https://rpc.aurpay.net/docs/providers/chainstack.md) | Yes | Yes |
| [dRPC](https://rpc.aurpay.net/docs/providers/drpc.md) | Yes | Yes |
| [Tenderly](https://rpc.aurpay.net/docs/providers/tenderly.md) | Yes | Yes |

All five integrations cover both Arbitrum networks, so a Route can mix upstreams from several vendors that answer the same reads.

## Reads without an Endpoint

Arbitrum uses the EVM Endpoint-free set: `eth_blockNumber`, `eth_getBlockByNumber` with `["latest", false]` or an explicit hexadecimal height and `false`, and `debug_traceBlockByNumber` with the `callTracer` configuration. Heights refer to Arbitrum block numbers, not L1 blocks. Other parameter variants require a Route; [Endpoint-free RPC](https://rpc.aurpay.net/docs/endpoint-free-rpc.md) documents the exact forms and cache behavior.

## Verify the network

```bash
curl '<arbitrum_access_point>' \
  -H 'Authorization: Bearer <app_api_key>' \
  -H 'Content-Type: application/json' \
  --data '{"jsonrpc":"2.0","id":1,"method":"eth_chainId","params":[]}'
```

Mainnet returns `0xa4b1`; Sepolia returns `0x66eee`.

## Coverage boundary

One JSON-RPC 2.0 object per HTTP `POST`. Arbitrum-specific namespaces, trace support, and historical state come from the upstream node; the Gateway routes them but adds no methods of its own.

See [Routing and reliability](https://rpc.aurpay.net/docs/reliability.md) for strategy details and [Errors and recovery](https://rpc.aurpay.net/docs/errors.md) for Gateway error codes.