eth_getStorageAt | Base RPC Docs

Read the value from a storage slot at a given contract address on Base. Essential for reading contract state directly, proxy implementation verification, and storage layout analysis.

Returns the value from a storage position at a given address on Base. This provides direct access to the raw EVM storage of any smart contract, bypassing ABI encoding and public getter functions.

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When to Use This Method

eth_getStorageAt is essential for consumer app developers, SocialFi builders, and teams seeking easy fiat onramps:

Reading Private State — Access contract state variables that have no public getter, including variables marked as private or internal in Solidity
Proxy Implementation Verification — Read the implementation address from EIP-1967 proxy storage slots to verify which logic contract a proxy delegates to on consumer dApps, SocialFi, NFT marketplaces, and merchant payment integrations
Storage Layout Analysis — Inspect raw storage slots for security auditing, debugging, or reverse-engineering contract behavior
State Change Monitoring — Track specific storage slot changes across blocks to monitor protocol parameters, admin roles, or balances

Code Examples

Common Use Cases

1. Verify Proxy Implementation Address

Read the EIP-1967 implementation slot to verify which contract a proxy points to on Base:

JavaScript

import { JsonRpcProvider, keccak256, toUtf8Bytes } from 'ethers';

const provider = new JsonRpcProvider('https://api-base-mainnet-archive.n.dwellir.com/YOUR_API_KEY');

async function getProxyImplementation(proxyAddress) {
  // EIP-1967 implementation slot:
  // bytes32(uint256(keccak256('eip1967.proxy.implementation')) - 1)
  const EIP1967_IMPL_SLOT = '0x360894a13ba1a3210667c828492db98dca3e2076cc3735a920a3ca505d382bbc';

  const value = await provider.getStorage(proxyAddress, EIP1967_IMPL_SLOT);

  // Extract the address from the 32-byte value (last 20 bytes)
  const implAddress = '0x' + value.slice(26);

  if (implAddress === '0x' + '0'.repeat(40)) {
    console.log('Not a standard EIP-1967 proxy or no implementation set');
    return null;
  }

  console.log(`Proxy: ${proxyAddress}`);
  console.log(`Implementation: ${implAddress}`);
  return implAddress;
}

// Also check the admin slot
async function getProxyAdmin(proxyAddress) {
  const EIP1967_ADMIN_SLOT = '0xb53127684a568b3173ae13b9f8a6016e243e63b6e8ee1178d6a717850b5d6103';
  const value = await provider.getStorage(proxyAddress, EIP1967_ADMIN_SLOT);
  return '0x' + value.slice(26);
}

2. Read Solidity Mapping Values

Calculate the storage slot for a mapping entry and read it:

JavaScript

import { JsonRpcProvider, keccak256, AbiCoder, zeroPadValue, toBeHex } from 'ethers';

const provider = new JsonRpcProvider('https://api-base-mainnet-archive.n.dwellir.com/YOUR_API_KEY');

async function readMapping(contractAddress, mappingSlot, key) {
  // For mapping(address => uint256) at slot N:
  // slot = keccak256(abi.encode(key, N))
  const abiCoder = AbiCoder.defaultAbiCoder();
  const encoded = abiCoder.encode(
    ['address', 'uint256'],
    [key, mappingSlot]
  );
  const slot = keccak256(encoded);

  const value = await provider.getStorage(contractAddress, slot);
  return BigInt(value);
}

// Example: read an ERC-20 balance (balanceOf mapping is typically at slot 0 or 1)
const contractAddress = '0x4200000000000000000000000000000000000006';
const holderAddress = '0x1234567890abcdef1234567890abcdef12345678';
const balance = await readMapping(contractAddress, 0, holderAddress);
console.log('Token balance:', balance.toString());

3. Storage Layout Inspector

Scan multiple storage slots to analyze a contract's state:

JavaScript

async function inspectStorage(provider, address, slotCount = 10) {
  console.log(`Inspecting storage for ${address} on Base:`);
  console.log('─'.repeat(80));

  const results = [];
  for (let i = 0; i < slotCount; i++) {
    const value = await provider.getStorage(address, i);
    const isZero = value === '0x' + '0'.repeat(64);

    if (!isZero) {
      // Try to interpret the value
      const asNumber = BigInt(value);
      const asAddress = '0x' + value.slice(26);
      const hasAddressPattern = value.slice(2, 26) === '0'.repeat(24);

      console.log(`Slot ${i}: ${value}`);
      if (hasAddressPattern && asAddress !== '0x' + '0'.repeat(40)) {
        console.log(`  → Possible address: ${asAddress}`);
      } else {
        console.log(`  → As uint256: ${asNumber}`);
      }

      results.push({ slot: i, value, asNumber });
    }
  }

  return results;
}

Error Handling

Common errors and solutions:

Error Code	Description	Solution
-32602	Invalid params	Verify the address is a valid 20-byte hex string, position is a valid hex quantity, and block parameter is valid
-32603	Internal error	Retry with exponential backoff
-32000	Execution error	The requested block may be pruned — try `latest` or a more recent block
-32005	Rate limit exceeded	Implement caching and reduce request frequency

JavaScript

async function safeGetStorage(provider, address, slot, maxRetries = 3) {
  for (let i = 0; i < maxRetries; i++) {
    try {
      return await provider.getStorage(address, slot);
    } catch (error) {
      if (error.code === -32000) {
        // Block may be pruned — try latest
        return await provider.getStorage(address, slot, 'latest');
      }
      if (error.code === -32005) {
        await new Promise(r => setTimeout(r, Math.pow(2, i) * 1000));
        continue;
      }
      if (i === maxRetries - 1) throw error;
      await new Promise(r => setTimeout(r, Math.pow(2, i) * 1000));
    }
  }
}

eth_call — Execute a contract function call without a transaction
eth_getCode — Get the bytecode deployed at an address
eth_getBalance — Get the ETH balance of an address
eth_getBlockByNumber — Get block details for historical storage queries

eth_getStorageAt - Base RPC Method

When to Use This Method

Code Examples

Common Use Cases

1. Verify Proxy Implementation Address

2. Read Solidity Mapping Values

3. Storage Layout Inspector

Error Handling

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