---
title: "Base JSON-RPC API Reference"
sidebar_position: 21
tags: [Base, EVM, JSON-RPC, blockchain, API]
keywords: [Base RPC, Base API, BASE, EVM, blockchain infrastructure, smart contracts, Web3]
description: "Base is an Ethereum Layer 2 (L2) network developed by Coinbase, designed for secure, low-cost, builder-friendly applications with seamless integration"
last_updated: 2026-08-19
---

# Base JSON-RPC API Reference

bex.co provides comprehensive support for the Base JSON-RPC specification, including all standard methods plus debug and trace APIs for advanced use cases. This reference covers all available methods with detailed parameters, return values, and code examples.

## Standard RPC Methods

### Account & Balance Methods

#### eth_getBalance

Get the balance of an account at a given block.

**Parameters:**
1. `address` (string) - 20-byte address to check for balance
2. `blockNumber` (string) - Block number in hex, or "latest", "earliest", "pending"

**Returns:** Balance in wei as a hex string

```bash
curl -X POST https://api.bex.co/base/${accessKey} \
  -H "Content-Type: application/json" \
  -d '{
    "jsonrpc": "2.0",
    "method": "eth_getBalance",
    "params": ["0x742D5Cc6bF2442E8C7c74c7b4Be6AB9d6f10f5B4", "latest"],
    "id": 1
  }'
```

```javascript
// Using Web3.js
const balance = await web3.eth.getBalance('0x742D5Cc6bF2442E8C7c74c7b4Be6AB9d6f10f5B4');

// Using Ethers.js
const balance = await provider.getBalance('0x742D5Cc6bF2442E8C7c74c7b4Be6AB9d6f10f5B4');
```

#### eth_getTransactionCount

Get the number of transactions sent from an address (nonce).

**Parameters:**
1. `address` (string) - 20-byte address
2. `blockNumber` (string) - Block number in hex, or "latest", "earliest", "pending"

**Returns:** Transaction count as hex string

```bash
curl -X POST https://api.bex.co/base/${accessKey} \
  -H "Content-Type: application/json" \
  -d '{
    "jsonrpc": "2.0",
    "method": "eth_getTransactionCount",
    "params": ["0x742D5Cc6bF2442E8C7c74c7b4Be6AB9d6f10f5B4", "latest"],
    "id": 1
  }'
```

#### eth_getCode

Get the code at a given address.

**Parameters:**
1. `address` (string) - 20-byte address
2. `blockNumber` (string) - Block number in hex, or "latest", "earliest", "pending"

**Returns:** Code as hex string

```bash
curl -X POST https://api.bex.co/base/${accessKey} \
  -H "Content-Type: application/json" \
  -d '{
    "jsonrpc": "2.0",
    "method": "eth_getCode",
    "params": ["0xA0b86a33E6c0e4A2a2a5FB1C6A6D6a30BF8b6B3a", "latest"],
    "id": 1
  }'
```

### Block Methods

#### eth_blockNumber

Get the current block number.

**Parameters:** None

**Returns:** Current block number as hex string

```bash
curl -X POST https://api.bex.co/base/${accessKey} \
  -H "Content-Type: application/json" \
  -d '{
    "jsonrpc": "2.0",
    "method": "eth_blockNumber",
    "params": [],
    "id": 1
  }'
```

#### eth_getBlockByNumber

Get block information by block number.

**Parameters:**
1. `blockNumber` (string) - Block number in hex, or "latest", "earliest", "pending"
2. `fullTransactions` (boolean) - If true, returns full transaction objects; if false, only hashes

**Returns:** Block object or null

```bash
curl -X POST https://api.bex.co/base/${accessKey} \
  -H "Content-Type: application/json" \
  -d '{
    "jsonrpc": "2.0",
    "method": "eth_getBlockByNumber",
    "params": ["latest", true],
    "id": 1
  }'
```

#### eth_getBlockByHash

Get block information by block hash.

**Parameters:**
1. `blockHash` (string) - 32-byte block hash
2. `fullTransactions` (boolean) - If true, returns full transaction objects; if false, only hashes

**Returns:** Block object or null

```bash
curl -X POST https://api.bex.co/base/${accessKey} \
  -H "Content-Type: application/json" \
  -d '{
    "jsonrpc": "2.0",
    "method": "eth_getBlockByHash",
    "params": ["0x1234567890abcdef1234567890abcdef1234567890abcdef1234567890abcdef", false],
    "id": 1
  }'
```

### Transaction Methods

#### eth_getTransactionByHash

Get transaction information by transaction hash.

**Parameters:**
1. `transactionHash` (string) - 32-byte transaction hash

**Returns:** Transaction object or null

```bash
curl -X POST https://api.bex.co/base/${accessKey} \
  -H "Content-Type: application/json" \
  -d '{
    "jsonrpc": "2.0",
    "method": "eth_getTransactionByHash",
    "params": ["0x1234567890abcdef1234567890abcdef1234567890abcdef1234567890abcdef"],
    "id": 1
  }'
```

#### eth_getTransactionReceipt

Get transaction receipt by transaction hash.

**Parameters:**
1. `transactionHash` (string) - 32-byte transaction hash

**Returns:** Transaction receipt object or null

```bash
curl -X POST https://api.bex.co/base/${accessKey} \
  -H "Content-Type: application/json" \
  -d '{
    "jsonrpc": "2.0",
    "method": "eth_getTransactionReceipt",
    "params": ["0x1234567890abcdef1234567890abcdef1234567890abcdef1234567890abcdef"],
    "id": 1
  }'
```

#### eth_sendRawTransaction

Submit a signed transaction to the network.

**Parameters:**
1. `signedTransaction` (string) - Signed transaction data as hex string

**Returns:** Transaction hash

```bash
curl -X POST https://api.bex.co/base/${accessKey} \
  -H "Content-Type: application/json" \
  -d '{
    "jsonrpc": "2.0",
    "method": "eth_sendRawTransaction",
    "params": ["0xf86c808504a817c800825208943535353535353535353535353535353535353535880de0b6b3a76400008025a04f4c17305743700648bc4f6cd3038ec6f6af0df73e31757d8a17c7e9e1f3c7fd2a053a8ffdc8ab1f4b5a1e4d9b4a2c3a6b4a6e1e8c4b4d6c6d6e1b4a6e1e8c4b4"],
    "id": 1
  }'
```

### Smart Contract Interaction

#### eth_call

Execute a smart contract function call without creating a transaction.

**Parameters:**
1. `callObject` (object) - Call parameters
   - `to` (string) - Contract address
   - `data` (string) - Encoded function call data
   - `from` (string, optional) - Sender address
   - `gas` (string, optional) - Gas limit
   - `gasPrice` (string, optional) - Gas price
   - `value` (string, optional) - Value to send
2. `blockNumber` (string) - Block number in hex, or "latest", "earliest", "pending"

**Returns:** Return value of the call

```bash
curl -X POST https://api.bex.co/base/${accessKey} \
  -H "Content-Type: application/json" \
  -d '{
    "jsonrpc": "2.0",
    "method": "eth_call",
    "params": [
      {
        "to": "0xA0b86a33E6c0e4A2a2a5FB1C6A6D6a30BF8b6B3a",
        "data": "0x70a08231000000000000000000000000742D5Cc6bF2442E8C7c74c7b4Be6AB9d6f10f5B4"
      },
      "latest"
    ],
    "id": 1
  }'
```

#### eth_estimateGas

Estimate gas needed for a transaction.

**Parameters:**
1. `transactionObject` (object) - Transaction parameters
   - `to` (string, optional) - Recipient address
   - `from` (string, optional) - Sender address
   - `data` (string, optional) - Transaction data
   - `value` (string, optional) - Value to send
   - `gas` (string, optional) - Gas limit
   - `gasPrice` (string, optional) - Gas price

**Returns:** Estimated gas amount as hex string

```bash
curl -X POST https://api.bex.co/base/${accessKey} \
  -H "Content-Type: application/json" \
  -d '{
    "jsonrpc": "2.0",
    "method": "eth_estimateGas",
    "params": [
      {
        "to": "0x742D5Cc6bF2442E8C7c74c7b4Be6AB9d6f10f5B4",
        "value": "0xde0b6b3a7640000"
      }
    ],
    "id": 1
  }'
```

### Gas and Fee Methods

#### eth_gasPrice

Get current gas price.

**Parameters:** None

**Returns:** Current gas price in wei as hex string

```bash
curl -X POST https://api.bex.co/base/${accessKey} \
  -H "Content-Type: application/json" \
  -d '{
    "jsonrpc": "2.0",
    "method": "eth_gasPrice",
    "params": [],
    "id": 1
  }'
```

#### eth_feeHistory

Get fee history for a range of blocks (EIP-1559).

**Parameters:**
1. `blockCount` (string) - Number of blocks to return fee history for
2. `newestBlock` (string) - Block number in hex, or "latest", "earliest", "pending"
3. `rewardPercentiles` (array) - Array of percentiles to return (0-100)

**Returns:** Fee history object

```bash
curl -X POST https://api.bex.co/base/${accessKey} \
  -H "Content-Type: application/json" \
  -d '{
    "jsonrpc": "2.0",
    "method": "eth_feeHistory",
    "params": ["10", "latest", [25, 50, 75]],
    "id": 1
  }'
```

#### eth_maxPriorityFeePerGas

Get suggested max priority fee per gas for EIP-1559 transactions.

**Parameters:** None

**Returns:** Suggested max priority fee per gas as hex string

```bash
curl -X POST https://api.bex.co/base/${accessKey} \
  -H "Content-Type: application/json" \
  -d '{
    "jsonrpc": "2.0",
    "method": "eth_maxPriorityFeePerGas",
    "params": [],
    "id": 1
  }'
```

### Log and Event Methods

#### eth_getLogs

Get logs matching a filter.

**Parameters:**
1. `filterObject` (object) - Filter parameters
   - `fromBlock` (string, optional) - Starting block
   - `toBlock` (string, optional) - Ending block
   - `address` (string|array, optional) - Contract address(es)
   - `topics` (array, optional) - Array of topic filters
   - `blockHash` (string, optional) - Block hash (cannot be used with fromBlock/toBlock)

**Returns:** Array of log objects

```bash
curl -X POST https://api.bex.co/base/${accessKey} \
  -H "Content-Type: application/json" \
  -d '{
    "jsonrpc": "2.0",
    "method": "eth_getLogs",
    "params": [
      {
        "fromBlock": "0x1",
        "toBlock": "latest",
        "address": "0xA0b86a33E6c0e4A2a2a5FB1C6A6D6a30BF8b6B3a",
        "topics": ["0xddf252ad1be2c89b69c2b068fc378daa952ba7f163c4a11628f55a4df523b3ef"]
      }
    ],
    "id": 1
  }'
```

### Network Information

#### eth_chainId

Get the chain ID of the current network.

**Parameters:** None

**Returns:** Chain ID as hex string

```bash
curl -X POST https://api.bex.co/base/${accessKey} \
  -H "Content-Type: application/json" \
  -d '{
    "jsonrpc": "2.0",
    "method": "eth_chainId",
    "params": [],
    "id": 1
  }'
```

#### net_version

Get the network ID.

**Parameters:** None

**Returns:** Network ID as string

```bash
curl -X POST https://api.bex.co/base/${accessKey} \
  -H "Content-Type: application/json" \
  -d '{
    "jsonrpc": "2.0",
    "method": "net_version",
    "params": [],
    "id": 1
  }'
```

## Debug & Trace Methods

### Debug Methods

#### debug_traceTransaction

Trace a transaction and return detailed execution information.

**Parameters:**
1. `transactionHash` (string) - Transaction hash to trace
2. `options` (object, optional) - Trace options
   - `tracer` (string) - Type of tracer ("callTracer", "prestateTracer", etc.)
   - `timeout` (string) - Timeout for trace execution

**Returns:** Trace result object

```bash
curl -X POST https://api.bex.co/base/${accessKey} \
  -H "Content-Type: application/json" \
  -d '{
    "jsonrpc": "2.0",
    "method": "debug_traceTransaction",
    "params": [
      "0x1234567890abcdef1234567890abcdef1234567890abcdef1234567890abcdef",
      {"tracer": "callTracer"}
    ],
    "id": 1
  }'
```

#### debug_traceBlock

Trace all transactions in a block.

**Parameters:**
1. `blockNumber` (string) - Block number in hex, or "latest"
2. `options` (object, optional) - Trace options

**Returns:** Array of trace results for each transaction

```bash
curl -X POST https://api.bex.co/base/${accessKey} \
  -H "Content-Type: application/json" \
  -d '{
    "jsonrpc": "2.0",
    "method": "debug_traceBlock",
    "params": ["latest", {"tracer": "callTracer"}],
    "id": 1
  }'
```

### Trace Methods

#### trace_transaction

Get trace information for a transaction.

**Parameters:**
1. `transactionHash` (string) - Transaction hash to trace

**Returns:** Array of trace objects

```bash
curl -X POST https://api.bex.co/base/${accessKey} \
  -H "Content-Type: application/json" \
  -d '{
    "jsonrpc": "2.0",
    "method": "trace_transaction",
    "params": ["0x1234567890abcdef1234567890abcdef1234567890abcdef1234567890abcdef"],
    "id": 1
  }'
```

#### trace_block

Get traces for all transactions in a block.

**Parameters:**
1. `blockNumber` (string) - Block number in hex, or "latest"

**Returns:** Array of trace objects for all transactions in the block

```bash
curl -X POST https://api.bex.co/base/${accessKey} \
  -H "Content-Type: application/json" \
  -d '{
    "jsonrpc": "2.0",
    "method": "trace_block",
    "params": ["latest"],
    "id": 1
  }'
```

## Batch Requests

You can send multiple RPC calls in a single HTTP request using JSON-RPC batch format:

```bash
curl -X POST https://api.bex.co/base/${accessKey} \
  -H "Content-Type: application/json" \
  -d '[
    {
      "jsonrpc": "2.0",
      "method": "eth_blockNumber",
      "params": [],
      "id": 1
    },
    {
      "jsonrpc": "2.0",
      "method": "eth_gasPrice",
      "params": [],
      "id": 2
    },
    {
      "jsonrpc": "2.0",
      "method": "eth_getBalance",
      "params": ["0x742D5Cc6bF2442E8C7c74c7b4Be6AB9d6f10f5B4", "latest"],
      "id": 3
    }
  ]'
```

## Error Handling

### Common Error Codes

| Code | Message | Description |
|------|---------|-------------|
| -32700 | Parse error | Invalid JSON |
| -32600 | Invalid Request | JSON-RPC request is invalid |
| -32601 | Method not found | Method does not exist |
| -32602 | Invalid params | Invalid method parameters |
| -32603 | Internal error | Internal JSON-RPC error |
| -32000 | Server error | Base execution error |

### Example Error Response

```json
{
  "jsonrpc": "2.0",
  "error": {
    "code": -32602,
    "message": "Invalid params",
    "data": "Invalid address format"
  },
  "id": 1
}
```

### Error Handling in Code

```javascript
async function handleRpcCall(method, params) {
  try {
    const response = await fetch(endpoint, {
      method: 'POST',
      headers: { 'Content-Type': 'application/json' },
      body: JSON.stringify({
        jsonrpc: '2.0',
        method,
        params,
        id: 1
      })
    });
    
    const data = await response.json();
    
    if (data.error) {
      throw new Error(`RPC Error ${data.error.code}: ${data.error.message}`);
    }
    
    return data.result;
  } catch (error) {
    console.error('RPC call failed:', error);
    throw error;
  }
}
```

## Performance Tips

### 1. Use Batch Requests
Combine multiple calls into a single request to reduce latency:

```javascript
const batchRequest = [
  { jsonrpc: '2.0', method: 'eth_blockNumber', params: [], id: 1 },
  { jsonrpc: '2.0', method: 'eth_gasPrice', params: [], id: 2 }
];
```

### 2. Cache Results
Cache responses for data that doesn't change frequently:

```javascript
const cache = new Map();

async function getCachedBalance(address) {
  const cacheKey = `balance:${address}`;
  if (cache.has(cacheKey)) {
    return cache.get(cacheKey);
  }
  
  const balance = await getBalance(address);
  cache.set(cacheKey, balance);
  setTimeout(() => cache.delete(cacheKey), 60000); // 1 minute cache
  
  return balance;
}
```

### 3. Use WebSockets for Real-time Data
For continuous monitoring, WebSockets are more efficient than polling:

```javascript
const ws = new WebSocket('wss://api.bex.co/base/${accessKey}');

ws.send(JSON.stringify({
  jsonrpc: '2.0',
  method: 'eth_subscribe',
  params: ['newHeads'],
  id: 1
}));
```

## Chain-Specific Features

### Mainnet Features
- Full archive node access
- Debug and trace APIs
- MEV protection
- Flashbot integration

### Testnet Features
- Faucet integration
- Development tools
- Fast sync options
- Reset capabilities

### Layer 2 Features
- Optimistic rollup support
- Arbitrum-specific methods
- Polygon gas station
- Cross-chain messaging

## Next Steps

- Learn about [WebSocket Connections]./base-websockets.md for real-time data streaming
- Explore [Web3.js Integration]./base-web3-integration.md for JavaScript development
- Check out [Ethers.js Integration]./base-ethers-integration.md for modern web development
- Follow smart contract interaction patterns for advanced use cases

## Resources

- [Base JSON-RPC Specification](https://ethereum.github.io/execution-apis/api-documentation/)
- [EIP-1559 Gas Fee Market](https://eips.ethereum.org/EIPS/eip-1559)
- [Debug & Trace APIs](https://geth.ethereum.org/docs/developers/evm-tracing)
- [bex.co API Dashboard](https://bex.co/dash/)

---

**Cost**: 300 CUs / req