Flashblocks

• Payments: Instant payment confirmations
• DeFi: Swaps and positions that update immediately
• Marketplaces: Fast, frictionless checkout flows
• Games: Real-time actions with no waiting between moves

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How it works

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Integrate Flashblocks

• In production, point your app to a Flashblocks‑aware RPC endpoint from your provider of choice. If your provider doesn’t support flashblocks yet, let us know on Discord and we’ll work with them to get it added.
• Alternatively, you can run your own flashblocks-aware node using Base’s reth image.

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Supported RPC methods

• eth_getBlockByNumber: Use the pending tag to retrieve the latest flashblock snapshot.

  Show Sample response

      {
        "jsonrpc": "2.0",
        "id": 1,
        "result": {
          "number": "0x1234",
          "hash": "0x...",
          "transactions": [...]
        }
      }
  
• eth_call: Use the pending tag to execute calls against the most recent pre-confirmed state.

  Show Sample request

  {
    "jsonrpc": "2.0",
    "method": "eth_call",
    "params": [{"to": "0x...", "data": "0x..."}, "pending"],
    "id": 1
  }
  
• eth_getBalance / eth_getTransactionCount: Use the pending tag to fetch balances or transaction counts as they evolve within the block window.

  Show Sample response for `eth_getBalance`

  {
    "jsonrpc": "2.0",
    "id": 1,
    "result": "0x0234"
  }
  

  Show Sample response for `eth_getTransactionCount`

  {
    "jsonrpc": "2.0",
    "id": 1,
    "result": "0x1b" // 27 transactions
  }
  
  Other methods, like eth_getTransactionReceipt and eth_getTransactionByHash, return data from pre-confirmed transactions without requiring the pending tag. Consult the Flashblocks specification for more details on each of these methods.

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Libraries

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Viem

import { createPublicClient, createWalletClient, http, parseEther } from 'viem';
import { privateKeyToAccount } from 'viem/accounts';
import { opSepolia } from 'viem/chains';
import { publicActionsL2, walletActionsL2 } from 'viem/op-stack';

const account = privateKeyToAccount(`0x${process.env.PRIVATE_KEY}`);

const walletClient = createWalletClient({
  account,
  chain: opSepolia,
  transport: http("https://sepolia.optimism.io"),
}).extend(walletActionsL2());

const publicClient = createPublicClient({
  chain: opSepolia,
  transport: http("https://sepolia.optimism.io"),
}).extend(publicActionsL2());

const submissionTime = new Date();
const hash = await walletClient.sendTransaction({
  to: '0x...',
  value: parseEther('0.0001'),
});

// Wait for pre-confirmation
const receipt = await publicClient.waitForTransactionReceipt({ hash });
const confirmTime = new Date();
console.log('pre-confirmed in ms:', confirmTime.getTime() - submissionTime.getTime());

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Ethers

import { ethers } from 'ethers';

// Here, provider is a Flashblocks-enabled RPC provider
const provider = new ethers.JsonRpcProvider("https://sepolia.optimism.io");
const wallet = new ethers.Wallet(process.env.PRIVATE_KEY as string, provider);

const tx = { to: '0x...', value: ethers.parseEther('0.0001') };
const submission = new Date();

const sent = await wallet.sendTransaction(tx);

await sent.wait(0);
const confirmed = new Date();

// should represent the transaction (pre)confirmation faster than standard RPC
console.log('Pre-confirmed in ms:', confirmed.getTime() - submission.getTime()); 

// validates the transaction hash returned by the pre-confirmed transaction above
const receipt = await provider.getTransactionReceipt(sent.hash);
console.log('Receipt validated in ms:', validated.getTime() - submission.getTime());
console.log('Transaction receipt:', receipt); 

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Flashblocks FAQ

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Block building and availability

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High availability and safety

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Pre-confirmations and reorgs

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Next steps

• Explore the high-level guide for operators.
• Review the technical specs for architecture details.
• Join our community to share best practices and get support!