debug_traceBlockByNumber

debug_traceBlockByNumber replays every transaction in an Arbitrum One block selected by its hex block number or a tag like latest, returning an opcode-level trace for each transaction in block order. Arbitrum One is a Nitro Optimistic Rollup (chain ID 42161) that settles to Ethereum L1 and meters gas in ETH, so block numbers advance quickly under the sequencer's sub-second confirmations. This is the convenient variant when you are walking the chain by height rather than chasing a specific hash. Send requests to https://arbitrum.therpc.io/YOUR_API_KEY with an optional tracer config.

Use cases

• Trace all transactions at a given Arbitrum One height to audit every state transition in one request while indexing the chain sequentially.
• Extract the full call graph of a block with callTracer for MEV research across the Arbitrum DeFi ecosystem (GMX, Uniswap, Aave).
• Compare the gas profile of every transaction in a block to spot outliers, keeping in mind Arbitrum fees split L2 execution cost from L1 calldata posting cost.

Parameters

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": "debug_traceBlockByNumber",
7    "params": [
8        "latest",
9        {}
10      ],
11    "id": 1
12  }'

Try it live in the Arbitrum One playground.

Errors & troubleshooting

Common pitfalls

• Tracing a whole block replays every transaction in it; a busy Arbitrum One block can take minutes and stream back gigabytes with the default struct logger.
• Historical blocks need an archive node with the matching ArbOS state; a pruned node only serves recent state and rejects older heights.
• Tags like latest are valid but race with the sequencer's fast-moving head — between resolving the tag and tracing, a new block may already be the latest.

Supported networks

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

See also

• debug_traceBlockByHash
• debug_traceBlock
• debug_traceTransaction
• trace_block

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":"debug_traceBlockByNumber","params":["latest",{}]}'