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# debug_traceCall

# `debug_traceCall`

Tracer is required

On `rpc.linea.build`, the default tracer is **not supported**. You must specify a tracer in the options object. Supported tracers are `callTracer` and `prestateTracer`. `flatCallTracer` is not supported.

Simulates a call at a given block and returns the trace, without submitting a transaction. Useful for debugging contract interactions before sending them.

## Parameters

-   `transaction`: _[required]_ Transaction call object (same fields as [`eth_call`](/api/reference/eth-call)).
-   `blockParameter`: _[required]_ Hexadecimal block number, or `latest`, `earliest`, `pending`, `finalized`.
-   `options`: _[required]_ Object specifying the tracer:
    -   `tracer`: _[required]_ `"callTracer"` or `"prestateTracer"`.

## Returns

Same trace output as [`debug_traceTransaction`](/api/reference/debug-tracetransaction), but for a simulated call.

## Example: `callTracer`

This example simulates `balanceOf(address)` on the USDC contract.

### Request

```bash
curl https://rpc.linea.build \
  -X POST \
  -H "Content-Type: application/json" \
  -d '{
    "jsonrpc": "2.0",
    "method": "debug_traceCall",
    "params": [
      {
        "to": "0x176211869ca2b568f2a7d4ee941e073a821ee1ff",
        "data": "0x70a08231000000000000000000000000d8da6bf26964af9d7eed9e03e53415d37aa96045"
      },
      "latest",
      {"tracer": "callTracer"}
    ],
    "id": 1
  }'
```

### Response

```json
{
  "jsonrpc": "2.0",
  "id": 1,
  "result": {
    "from": "0x0000000000000000000000000000000000000000",
    "to": "0x176211869ca2b568f2a7d4ee941e073a821ee1ff",
    "gas": "0x2faf080",
    "gasUsed": "0x79b6",
    "input": "0x70a08231000000000000000000000000d8da6bf26964af9d7eed9e03e53415d37aa96045",
    "output": "0x000000000000000000000000000000000000000000000000000000000026009c",
    "calls": [
      {
        "from": "0x176211869ca2b568f2a7d4ee941e073a821ee1ff",
        "to": "0xab838fe7d492c621a5b1b23952af99cc37a2e0d3",
        "gas": "0x2ee96d1",
        "gasUsed": "0x9e1",
        "input": "0x70a08231000000000000000000000000d8da6bf26964af9d7eed9e03e53415d37aa96045",
        "output": "0x000000000000000000000000000000000000000000000000000000000026009c",
        "value": "0x0",
        "type": "DELEGATECALL"
      }
    ],
    "value": "0x0",
    "type": "CALL"
  }
}
```

`prestateTracer` is also supported and returns the pre-execution state of every account the call would touch, identical in shape to the [`debug_traceTransaction` `prestateTracer` response](/api/reference/debug-tracetransaction#example-prestatetracer).