trace_call

trace_call runs a call against a chosen block's state and traces it, without ever broadcasting a transaction. The result can include an OpenEthereum-style call-tree trace, an optional opcode-level VM trace, and an optional state diff. BSC settles in BNB and runs the BEP-20 contracts behind venues like PancakeSwap, so this is how you preview what a router or swap call would actually do before committing gas to it. Send the request to chain ID 56 at https://bsc.therpc.io/YOUR_API_KEY. The traceTypes array decides which artifacts get computed, keeping the response to the detail you asked for. Simulating against a past block pulls in historical state, which makes it a heavy call that needs a trace-enabled archive node.

Use cases

Map the full call tree a transaction would spawn before you broadcast it.
Ask for stateDiff to confirm a prospective transaction touches exactly the balances and storage slots you expect, and nothing more.
Test contract logic against a historical BSC block state, which calls for a trace-enabled archive node.

Parameters

#	Name	Type	Required	Description
1	`transaction`	object	Yes	Call object: `from?`, `to`, `gas?`, `gasPrice?`, `value?`, `data?`.
2	`traceTypes`	array	Yes	Array of trace types to include: `"trace"` (call tree), `"vmTrace"` (opcode-level), `"stateDiff"` (storage/balance diffs).
3	`blockParameter`	string	No	Block state against which to simulate the call.Default: `latest`

Response

Type	Description
object	`{output, trace?, stateDiff?, vmTrace?}` — `trace` is a flat call-tree array, `stateDiff` maps each touched address to its balance/nonce/code/storage diffs, `vmTrace` provides opcode-level detail (Parity-format).

Example request

1curl https://bsc.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 BNB Smart Chain playground.

Errors & troubleshooting

Code	Message	Cause
`-32601`	`Method not found`	trace namespace not enabled or client does not support trace_call.
`-32602`	`Invalid params`	Transaction object missing required fields, traceTypes array is empty or contains unrecognized values, or blockParameter is invalid.
`-32000`	`execution reverted`	Simulated call reverted; partial trace is still returned.

Common pitfalls

Asking for trace, vmTrace, and stateDiff together can balloon the response, so request only the artifacts you actually need.
Historical block states require a node running the trace API over archive data, which lower tiers may not provide.
The vmTrace output uses a Parity-specific shape that differs from the structLog Geth returns from debug_traceCall.

Supported networks

Mainnet — Chain ID: 56
Testnet — Chain ID: 97