Base RPC Overview

Complete reference for all JSON-RPC and Flashblocks methods available on Base nodes.

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

Network	Chain ID	Type	Archive
Mainnet	8453	Production	Yes
Sepolia	84532	Testnet	Yes

Endpoints

Mainnet

	HTTP
RPC	https://mainnet.base.org

Sepolia

	HTTP
RPC	https://sepolia.base.org

The public endpoints above are rate-limited and not suitable for production traffic. For production use, connect through a node provider.

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