eth_call

Execute a read-only call in the specified block state. eth_call will not create on-chain transactions and will not consume user Gas. It is often used to read contract status or pre-check contract call results.

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Inputs

Index	Type	Description
0	object	call object
1	string	Block number or label, such as latest, earliest, pending

Transaction call object

Field	Variant	Need	Remarks
to	string	yes	Contract address being called
data	string	no	ABI-encoded call data
from	string	no	Sender used for call-context simulation
gas	string	no	Gas limit encoded as hex
gasPrice	string	no	Gas price encoded as hex
value	string	no	Attached wei amount

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return value

string - ​​Contract return data, hexadecimal encoding.

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Demo

Read ERC-20 balance

// Method selector for balanceOf(address): 0x70a08231
const address = "0x1a2b3c4d5e6f708192a3b4c5d6e7f8091a2b3c4d".slice(2).padStart(64, "0");
const data = "0x70a08231" + address;

const balance = await window.$ukey.ethereum.request({
  method: "eth_call",
  requestParams: [
    {
      to: "0x2b4d6f8091a3c5e7f9b1d3f507192b4d6f8091a3", // Note: sample token contract
      data: data,
    },
    "latest",
  ],
});

console.log("Current balance:", parseInt(balance, 16));

Read contract name

// Method selector for name(): 0x06fdde03
const name = await window.$ukey.ethereum.request({
  method: "eth_call",
  requestParams: [
    {
      to: "0x2b4d6f8091a3c5e7f9b1d3f507192b4d6f8091a3",
      data: "0x06fdde03",
    },
    "latest",
  ],
});

// Decoded output from the ABI-encoded string
console.log("Decoded contract name:", decodeString(name));

Using ethers.js

import { Contract, BrowserProvider } from "ethers";

const provider = new BrowserProvider(window.$ukey.ethereum);

const contract = new Contract(
  "0x2b4d6f8091a3c5e7f9b1d3f507192b4d6f8091a3",
  ["function balanceOf(address) view returns (uint256)"],
  provider,
);

const balance = await contract.balanceOf("0x1a2b3c4d5e6f708192a3b4c5d6e7f8091a2b3c4d");
console.log("USDC token balance:", balance.toString());

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error code

Code	Message	Details
-32000	Execution reverted	Contract call rollback
-32602	Parameters failed validation	Invalid call inputs

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illustrate

• This method will not modify the on-chain status, nor will it initiate transaction confirmation to the user.
• from Although optional: some contracts will return different results depending on the caller address.
• Use latest to read the latest known status; if you need historical status, you can pass in a specific block.
• Leave complex ABI encoding and decoding to ethers.js, viem or web3.js.