debug_traceBlockByHash

debug_traceBlockByHash re-executes every transaction in one Arbitrum One block — identified by its 32-byte block hash — and returns an opcode-level trace for each, in block order. Arbitrum One is a Nitro Optimistic Rollup (chain ID 42161) whose sequencer gives sub-second soft confirmations and whose gas is paid in ETH; tracing by hash pins you to one exact block even across reorgs near the unsafe head. Pass an optional tracer config (callTracer, prestateTracer, or the default struct logger) and send the request to https://arbitrum.therpc.io/YOUR_API_KEY.

Use cases

• Deterministically trace one specific Arbitrum One block when you hold its hash, for example from a reorg investigation near the sequencer's unsafe head.
• Audit every internal call inside a known block — useful when reconciling indexer output against on-chain state from Arbiscan.
• Build a block-level call graph with callTracer for MEV analysis across GMX, Uniswap, and Camelot activity in a single block.

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_traceBlockByHash",
7    "params": [
8        "0x0000000000000000000000000000000000000000000000000000000000000000",
9        {}
10      ],
11    "id": 1
12  }'

Try it live in the Arbitrum One playground.

Errors & troubleshooting

Common pitfalls

• The cost is identical to debug_traceBlockByNumber: the node replays every transaction in the block, so a dense Arbitrum One block is far heavier than tracing a single transaction.
• Historical blocks require an archive node holding the matching ArbOS state; a pruned node returns "block not found" (-32000).
• Blocks packed with complex DeFi transactions can exceed the default tracer timeout on remote nodes — narrow your tracer config or use a compact tracer such as callTracer.

Supported networks

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

See also

• debug_traceBlockByNumber
• 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_traceBlockByHash","params":["0x0000000000000000000000000000000000000000000000000000000000000000",{}]}'