trace_call

trace_call simulates a call against a chosen Arbitrum One block state and returns an OpenEthereum-style result — a call-tree trace, an optional opcode-level vmTrace, and an optional stateDiff — all without creating a transaction or spending ETH. You choose which trace types to compute via the traceTypes array, so you can ask only for the storage and balance diffs, only for the call tree, or all three. Arbitrum One is a Nitro Optimistic Rollup (chain ID 42161) settling to Ethereum L1, and this runs through ArbOS exactly as a real call would. Send requests to https://arbitrum.therpc.io/YOUR_API_KEY.

Use cases

• Preview every internal call a transaction would generate on Arbitrum One before broadcasting it through the sequencer.
• Request stateDiff to validate that a prospective transaction changes exactly the storage and balances you expect — useful before a large Aave or GMX interaction.
• Test smart-contract logic against a historical Arbitrum One block state with the vmTrace type (past states require a trace-enabled archive node).

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": "trace_call",
7    "params": [
8        {
9          "to": "0x0000000000000000000000000000000000000000",
10          "data": "0x"
11        },
12        [
13          "trace"
14        ],
15        "latest"
16      ],
17    "id": 1
18  }'

Try it live in the Arbitrum One playground.

Errors & troubleshooting

Common pitfalls

• Requesting all three trace types at once (trace + vmTrace + stateDiff) can balloon the response on a complex Arbitrum One call — ask only for what you need.
• Simulating against a historical block state requires an archive node with the trace API enabled; most public Arbitrum endpoints do not offer it.
• The vmTrace format is Parity-specific and differs from Geth's debug_traceCall structLog — do not mix the two output shapes in your tooling.

Supported networks

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

See also

• trace_transaction
• debug_traceCall
• trace_replayTransaction
• trace_filter

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":"trace_call","params":[{"to":"0x0000000000000000000000000000000000000000","data":"0x"},[],"latest"]}'