eth_call - Optimism

Example code for the eth_call json-rpc method. Сomplete guide on how to use eth_call json-rpc in GetBlock.io Web3 documentation.

This method allows you to interact with smart contracts without sending a transaction or spending gas. It's commonly used to read data from contracts, such as checking token balances or calling view functions.

The eth_call method executes a read-only call to a smart contract on Optimism without consuming gas or modifying state.

Parameters

Parameter

Type

Description

Required

transaction

Object

Transaction call object with from (optional), to, gas (optional), gasPrice (optional), value (optional), and data fields.

Yes

block

QUANTITY|TAG

Block number in hex, or 'latest', 'earliest', 'pending'.

Yes

Request Sample

curl --location --request POST 'https://go.getblock.io/<ACCESS-TOKEN>/' \
--header 'Content-Type: application/json' \
--data-raw '{
    "jsonrpc": "2.0",
    "method": "eth_call",
    "params": [{"to": "0x4200000000000000000000000000000000000006", "data": "0x70a08231000000000000000000000000742d35Cc6634C0532925a3b844Bc9e7595f7bD5e"}, "latest"],
    "id": "getblock.io"
}'

import axios from 'axios';
const url = "https://go.getblock.io/<ACCESS-TOKEN>/";
const headers = { "Content-Type": "application/json" };

const payload = {
    jsonrpc: "2.0",
    method: "eth_call",
    params: [{"to": "0x4200000000000000000000000000000000000006", "data": "0x70a08231000000000000000000000000742d35Cc6634C0532925a3b844Bc9e7595f7bD5e"}, "latest"],
    id: "getblock.io"
};

axios.post(url, payload, { headers })
    .then(response => {
        if (response.status === 200) {
            console.log("eth_call result:", response.data.result);
        } else {
            console.error("Error:", response.status, response.statusText);
        }
    })
    .catch(error => {
        console.error("Error:", error.response ? error.response.data : error.message);
    });

import requests
import json

url = "https://go.getblock.io/<ACCESS-TOKEN>/"
headers = {
    "Content-Type": "application/json"
}
payload = {
    "jsonrpc": "2.0",
    "method": "eth_call",
    "params": [{"to": "0x4200000000000000000000000000000000000006", "data": "0x70a08231000000000000000000000000742d35Cc6634C0532925a3b844Bc9e7595f7bD5e"}, "latest"],
    "id": "getblock.io"
}

response = requests.post(url, headers=headers, data=json.dumps(payload))

if response.status_code == 200:
    result = response.json().get("result")
    print("eth_call result:", result)
else:
    print("Error:", response.status_code, response.text)

#[tokio::main]
async fn main() -> Result<(), Box<dyn std::error::Error>> {
    let client = reqwest::Client::builder()
        .build()?;

    let mut headers = reqwest::header::HeaderMap::new();
    headers.insert("Content-Type", "application/json".parse()?);

    let data = r#"{{
  "jsonrpc": "2.0",
  "method": "eth_call",
  "id": "getblock.io",
  "params": [
    {
      "to": "0x1F98431c8aD98523631AE4a59f267346ea31F984",
      "data": "0x8da5cb5b"
    },
    "latest"
  ]
}"#;

    let json: serde_json::Value = serde_json::from_str(&data)?;

    let request = client.request(reqwest::Method::POST, "https://go.getblock.us/<ACCESS_TOKEN>")
        .headers(headers)
        .json(&json);

    let response = request.send().await?;
    let body = response.text().await?;

    println!("{}", body);

    Ok(())
}

Response

A successful response returns the following:

{
    "jsonrpc": "2.0",
    "id": "getblock.io",
    "result": "0x000000000000000000000000ec23cf5a1db3dcc6595385d28b2a4d9b52503be4"
}

Response Parameters

id: A unique request identifier, matching the id sent in the request body.
jsonrpc: Specifies the use of JSON-RPC version 2.0.
result: The return value of the executed contract call as a hexadecimal string.

Use Case

The eth_call method is commonly used for:

Reading token balances
Calling view functions
Contract state inspection
Simulating transactions

Error handling

Status Code

Error Message

Cause

404

Not found

Missing or invalid ACCESS_TOKEN.

Integration with Web3

The eth_call can help developers to:

Enables trustless frontends
Reads live contract state without gas
Supports dashboards, DeFi analytics, wallets, NFT explorers
Let's developers simulate transactions before execution

import { ethers } from "ethers";
const RPC_URL = "https://go.getblock.us/24915a36b17143a891d3b10447615258";
const provider = new ethers.JsonRpcProvider(RPC_URL);
async function Call() {
  try {
    // Call the method — this will resolve to a number (promise resolves to number)
     const result = await provider.send("eth_call", [
       {
         to: "0x1F98431c8aD98523631AE4a59f267346ea31F984",
         data: "0x8da5cb5b",
       },
       "latest",
     ]);
    console.log("The result:", result);
    return result;
  } catch (error) {
    console.error("Ethers Error fetching block number:", error);
    throw error;
  }
}

import { useEffect, useState } from "react";
import { createPublicClient, http } from "viem";
import { optimism } from "viem/chains";


// Create Viem client with GetBlock
const client = createPublicClient({
  chain: optimism,
  transport: http("https://go.getblock.io/<ACCESS_TOKEN>
});
// Using the method through Viem
async function Call() {
  try {
 const result = await client.request({
   method: "eth_call",
   "params": [
    {
      "to": "0x1F98431c8aD98523631AE4a59f267346ea31F984",
      "data": "0x8da5cb5b"
    },
    "latest"
  ]
 });
 console.log("Response:", result);
 return result;
  }
   catch (error) {
 console.error("Viem Error:", error);
 throw error;
  }
}

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