Base RPC Overview

Base exposes a single, fully EVM-compatible JSON-RPC API across two performance tiers. You can move from 2-second block confirmations to 200ms pre-confirmations by switching one URL and one block tag.

Networks

For network details, RPC endpoints, and wallet setup, see Connecting to Base.

The public Base endpoints are HTTP only. WebSocket RPC connections (eth_subscribe, newHeads, logs) are not available on public Base endpoints — use a node provider such as Alchemy or QuickNode for WebSocket support.

Flashblocks

All Base public endpoints are Flashblocks-enabled. Every standard eth_ method works identically, and the pending block tag reflects the current pre-confirmed block in progress, updated every ~200ms with new batches of sequencer-ordered transactions. Calls like eth_getBalance, eth_getStorageAt, and eth_call run against real sequencer state up to 1.8 seconds before the block seals, with sub-second latency.

API Reference

Ethereum JSON-RPC API

Core Ethereum protocol methods for account queries, block and transaction data, gas estimation, and log filtering.

Methods marked ✓ support the "pending" block tag, which reflects the current pre-confirmed Flashblock in progress.

Method	Description	Flashblocks `pending`
eth_blockNumber	Current block number	—
eth_getBalance	Account ETH balance	✓
eth_getTransactionCount	Account nonce / tx count	✓
eth_getCode	Deployed contract bytecode	✓
eth_getStorageAt	Contract storage slot value	✓
eth_call	Execute read-only call	✓
eth_getBlockByNumber	Block data by number	✓
eth_getBlockByHash	Block data by hash	—
eth_getBlockReceipts	All receipts for a block	✓
eth_getBlockTransactionCountByNumber	Tx count by block number	✓
eth_getBlockTransactionCountByHash	Tx count by block hash	—
eth_getTransactionByHash	Transaction data by hash	—
eth_getTransactionByBlockHashAndIndex	Tx by block hash and index	—
eth_getTransactionByBlockNumberAndIndex	Tx by block number and index	—
eth_getTransactionReceipt	Receipt for a mined tx	—
eth_sendRawTransaction	Submit signed transaction	—
eth_gasPrice	Current gas price	—
eth_maxPriorityFeePerGas	Max priority fee estimate	—
eth_feeHistory	Historical base fee and rewards	—
eth_estimateGas	Estimate gas for a tx	✓
eth_getLogs	Query event logs by filter	✓
eth_chainId	Network chain ID	—
eth_syncing	Node sync status	—
net_version	Network version ID	—
web3_clientVersion	Client version string	—
eth_subscribe	Subscribe to events (WSS)	✓
eth_unsubscribe	Cancel a subscription (WSS)	—

Flashblocks API

Pre-confirmation methods for sub-second transaction signals on Base. These methods enable reading state, simulating bundles, and streaming events up to ~1.8 seconds before a block seals.

Method	Description
eth_simulateV1	Simulate transaction bundles against pre-confirmed state
base_transactionStatus	Check if a transaction has been received by the mempool
newFlashblockTransactions	Subscribe to individual pre-confirmed transactions
pendingLogs	Subscribe to filtered logs from pre-confirmed transactions
newFlashblocks	Subscribe to full Flashblock payload stream

Debug API

Development and debugging utilities for deep transaction inspection and block replay. Debug methods replay transactions and are computationally expensive — availability and rate limits vary by node provider.

Method	Description
debug_traceTransaction	Full EVM execution trace for a transaction
debug_traceBlockByHash	EVM traces for all transactions in a block by hash
debug_traceBlockByNumber	EVM traces for all transactions in a block by number

Request & Response Format

All requests are HTTP POST with Content-Type: application/json.

Field	Type	Description
`jsonrpc`	string	Always `"2.0"`
`method`	string	The RPC method name
`params`	array	Method parameters in order
`id`	number \| string	Identifier echoed back in the response

Request:

{
  "jsonrpc": "2.0",
  "method": "eth_getBalance",
  "params": ["0x742d35Cc6634C0532925a3b8D4C9dD0b4f3BaEa", "pending"],
  "id": 1
}

Success response:

{
  "jsonrpc": "2.0",
  "id": 1,
  "result": "0x1a055690d9db80000"
}

Error response:

{
  "jsonrpc": "2.0",
  "id": 1,
  "error": {
    "code": -32602,
    "message": "Invalid params"
  }
}

Error Codes

Code	Name	Description
`-32700`	Parse error	Invalid JSON
`-32600`	Invalid request	Not a valid JSON-RPC 2.0 object
`-32601`	Method not found	Method does not exist or is unavailable
`-32602`	Invalid params	Invalid method parameters
`-32603`	Internal error	Internal JSON-RPC error
`-32000`	Server error	Node-specific error (see message)

Block Parameters

Value	Standard	Flashblocks
`"latest"`	Most recently sealed block	Most recently sealed block
`"pending"`	Unmined transaction pool state	Current Flashblock in progress (~200ms resolution)
`"safe"`	Latest safe block	Latest safe block
`"finalized"`	Latest finalized block	Latest finalized block
`"earliest"`	Genesis block	Genesis block
`"0x<n>"`	Specific block by number	Specific block by number

Beryl Upgrade

Introduction

Core Concepts

Node Operators

Network Reference

API Reference

Protocol Specifications

Security

Networks

Flashblocks

API Reference

Ethereum JSON-RPC API

Flashblocks API

Debug API

Request & Response Format

Error Codes

Block Parameters

​Networks

​Flashblocks

​API Reference

​Ethereum JSON-RPC API

​Flashblocks API

​Debug API

​Request & Response Format

​Error Codes

​Block Parameters

Networks

Flashblocks

API Reference

Ethereum JSON-RPC API

Flashblocks API

Debug API

Request & Response Format

Error Codes

Block Parameters