eth_blockNumber

eth_blockNumber returns the height of the most recently sequenced L2 block on Arbitrum One, the Optimistic Rollup that settles to Ethereum and pays gas in ETH. Because the Nitro sequencer gives sub-second soft confirmations, this height climbs quickly — far faster than the underlying L1 batch cadence. Point it at https://arbitrum.therpc.io/YOUR_API_KEY (chain ID 42161) to read the current tip of the chain.

Use cases

• Heartbeat / liveness probe — the cheapest possible RPC call to confirm the Arbitrum One endpoint is reachable and the sequencer is producing blocks.
• Establish the current L2 height before paginating historical eth_getLogs ranges from a GMX or Uniswap deployment.
• Drive a "wait for N confirmations" loop in a deployment script targeting Arbiscan-verified contracts.
• Compare the returned height against a target block to judge how far behind a "finalized" anchor your reads are, given finality follows the L1 challenge window.

Parameters

Diese Methode erwartet keine Parameter. Übergib ein leeres Array [].

Response

Example request

1curl https://arbitrum.therpc.io/YOUR_API_KEY \
2  -X POST \
3  -H "Content-Type: application/json" \
4  -d '{
5    "jsonrpc": "2.0",
6    "method": "eth_blockNumber",
7    "params": [],
8    "id": 1
9  }'

Try it live in the Arbitrum One playground.

Errors & troubleshooting

Common pitfalls

• The return value is a hex string (e.g. "0xb71b00"), not a number — run it through parseInt(value, 16) or BigInt(value) before any arithmetic.
• Providers cache this value aggressively; two calls milliseconds apart may return the same height even though Arbitrum's sub-second blocks are still advancing.
• This is the Arbitrum One L2 block number, not the Ethereum L1 batch number the rollup posts to — do not cross-reference it against L1 block heights on Etherscan.

Supported networks

• Mainnet — Chain ID: 42161
• Sepolia — Chain ID: 421614

See also

• eth_getBlockByNumber
• eth_getBlockByHash
• eth_syncing
• eth_chainId

1curl https://arbitrum.therpc.io/YOUR_API_KEY \
2  -X POST \
3  -H 'Content-Type: application/json' \
4  -d '{"jsonrpc":"2.0","id":1,"method":"eth_blockNumber","params":[]}'