trace_call

trace_call simulates a call against a chosen Base block state and returns an OpenEthereum-style call-tree trace, plus an optional opcode-level VM trace and an optional state diff — all without creating or broadcasting a transaction. Base is Coinbase's OP Stack optimistic rollup that pays gas in ETH and settles to Ethereum L1. Send the request to https://base.therpc.io/YOUR_API_KEY (chain ID 8453, hex 0x2105) with a call object, a traceTypes array selecting which outputs you want (trace, vmTrace, stateDiff), and a block parameter. You choose how much detail to pay for: trace alone gives the call tree, while adding stateDiff shows exactly which balances and storage slots the call would touch.

Use cases

• Preview every internal call a Base transaction would generate before broadcasting it, by requesting the trace type on the call object.
• Diff the storage and balance changes a prospective Base transaction would make using stateDiff, to confirm it touches only the slots you expect.
• Test smart-contract logic against a historical Base block state by setting the block parameter to a past number (this requires an archive node with the trace API).

Parameters

Response

Example request

1curl https://base.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 Base playground.

Errors & troubleshooting

Common pitfalls

• Requesting all three trace types at once (trace + vmTrace + stateDiff) on a complex Base call can return a very large payload; ask only for the outputs you actually use.
• Simulating against a historical Base block state requires an archive node that also exposes the trace API; recent state works on a normal trace-enabled node.
• The vmTrace output uses the Parity format and differs from Geth's debug_traceCall struct-log — do not feed one into tooling that expects the other.

Supported networks

• Mainnet — Chain ID: 8453
• Sepolia — Chain ID: 84532

See also

• trace_transaction
• debug_traceCall
• trace_replayTransaction
• trace_filter

1curl https://base.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"]}'