debug_traceCall

Simulates a call and returns the output of a named tracer.

Geth reference · All supported methods

Parameters

Parameters are positional, in the order below.

Parameter	Type	Required	Description
transaction	Transaction object	Yes	Call fields such as from, to, data, value, and gas.
block	Block number or tag	Yes	State against which to simulate the call.
options	Trace options	Yes	Direct requires an explicit supported named tracer.

Transaction fields

Field	Meaning
from	Sender address used during execution
to	Destination address; omit for contract creation where supported
data or input	Encoded call data or contract creation code; use one field
value	Value transferred in wei, as a hexadecimal quantity
gas	Gas allowance for the simulation, as a hexadecimal quantity
gasPrice	Legacy gas price in wei; use instead of EIP-1559 fee fields
maxFeePerGas, maxPriorityFeePerGas	EIP-1559 fee limits in wei, where applicable
accessList	Addresses and storage keys supplied for execution

Tracing options

Field	Supported values
tracer	callTracer or prestateTracer; explicitly required by Direct
tracerConfig.onlyTopCall	Boolean for callTracer; omit or use false to include nested calls
tracerConfig.diffMode	Boolean for prestateTracer; use true for state changes, otherwise return accessed pre-state
timeout	Duration string such as 5s; cannot extend the gateway waiting deadline

Return value

The selected tracer’s result: a call-frame tree for callTracer, or account/state data for prestateTracer. diffMode returns pre- and post-execution changes.

Example

Replace <gateway-url> with your gateway base URL and <service-url> with the chain’s service path, such as service/ethereum.

curl -X POST "<gateway-url>/<service-url>" \
  -H "Content-Type: application/json" \
  --data '{"jsonrpc":"2.0","id":1,"method":"debug_traceCall","params":[{"to":"0x2222222222222222222222222222222222222222","data":"0x"},"latest",{"tracer":"callTracer"}]}'

Illustrative response; values depend on the selected network and request:

{
  "jsonrpc": "2.0",
  "id": 1,
  "result": {
    "type": "CALL",
    "from": "0x0000000000000000000000000000000000000000",
    "to": "0x2222222222222222222222222222222222222222",
    "value": "0x0",
    "gas": "0x1c9c380",
    "gasUsed": "0x0",
    "input": "0x",
    "output": "0x"
  }
}

Direct behavior

The gateway selects providers supporting the requested tracing group and format. Unsupported formats are rejected rather than replaced.

Specify tracer: "callTracer" with optional tracerConfig.onlyTopCall, or tracer: "prestateTracer" with optional tracerConfig.diffMode. Default opcode logging and arbitrary JavaScript tracers are not supported. An omitted tracer does not select a default output.

Historical simulations require archive state. Requests whose execution point is determined by latest follow the reference-block rules.

Limits

Simulations allow up to 30 million gas per call. Omitted gas uses that ceiling; an explicit higher allowance is rejected rather than silently reduced. State and block overrides are not included in the supported contract.

A debug timeout can request a shorter execution budget, but cannot extend the shared gateway deadline.

For providers

Qualify for the entire applicable tracing group, including required formats and options. Historical combinations are verified separately; recent success alone does not establish historical coverage.

See provider qualification for checks and continued eligibility.