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Overview

Flashblocks enable up to 200 millisecond transaction confirmations on Base by leveraging preconfirmations, ultra-fast signals that arrive before the next block is sealed. Built for developers who demand instant UX, it’s ideal for high-frequency apps, games, and real-time interactions where waiting even a few seconds is too long. By integrating directly within Base’s infrastructure, Flashblocks enables seamless, ultrafast and snappy user experiences without compromising security. See the Flashblocks API Reference for the full list of supported RPC methods and WebSocket subscription types.

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Integrating Flashblocks

Flashblocks is enabled for developers on Base. You can integrate with Flashblocks data via the RPC API or the WebSocket API.

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RPC Endpoints

Base offers the following public Flashblocks-aware RPC endpoints. These are rate-limited and may not be suitable for production use — we recommend using a node provider that runs Flashblocks-integrated nodes. Major node providers such as Alchemy, Infura, QuickNode, and dRPC have Flashblocks-aware RPCs.
NetworkURL
Mainnethttps://mainnet-preconf.base.org
Sepoliahttps://sepolia-preconf.base.org
For a full reference of all supported RPC methods — including preconfirmed state queries, simulation, and real-time subscriptions — see the Flashblocks API Reference.

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Libraries

You will need to use a Flashblocks-aware RPC endpoint to use Flashblocks with the following libraries:

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Wagmi

To use Flashblocks with Wagmi, you will need to use the basePreconf chain in the Wagmi Config (see config.ts). 
import { useSendTransaction, useWaitForTransactionReceipt } from "wagmi";

function SendTransaction() {
  const { data: hash, sendTransaction } = useSendTransaction();
  const { data: receipt } = useWaitForTransactionReceipt({ hash });

  return (
    <div>
      <button 
        onClick={() => sendTransaction({ 
          to: "0x...", 
          value: parseEther('0.0001'),
        })}
      >
        Send Transaction
      </button>
      {hash && <div>Hash: {hash}</div>}
      {receipt && <div>Included on block number: {receipt.blockNumber}</div>}
    </div>
  )
}

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Viem

import { createWalletClient, http, parseEther, publicActions } from "viem";
import { privateKeyToAccount } from "viem/accounts";
import { baseSepoliaPreconf } from "viem/chains";

// Create client with the Flashblocks-aware chain.
const account = privateKeyToAccount(`0x${process.env.PRIVATE_KEY}`);
const client = createWalletClient({
  account,
  chain: baseSepoliaPreconf,
  transport: http(),
})
  .extend(publicActions);

const submissionTime = new Date();
console.log(`Submitting transaction at: ${submissionTime.toISOString()}`);

// Send transaction.
const hash = await client.sendTransaction({
  to: "0x...",
  value: parseEther('0.0001'),
});
console.log(`Transaction hash: ${hash}`);

// Wait for transaction to be included.
const receipt = await client.waitForTransactionReceipt({ hash });
const confirmTime = new Date();

console.log(`Transaction included at: ${confirmTime.toISOString()}`);
console.log(`Time difference: ${confirmTime - submissionTime}ms`);

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Ethers

  const providerA = new ethers.JsonRpcProvider(
    "https://sepolia-preconf.base.org"
  );

  const wallet = new ethers.Wallet(process.env.PRIVATE_KEY, providerA);

  try {
    // Create a simple transaction (sending 0.001 ETH to a random address)
    const tx = {
      to: "<SOME ADDRESS>",
      value: ethers.parseEther("0.0000001"),
    };

    // Submit transaction
    const submissionTime = new Date();
    const transaction = await wallet.sendTransaction(tx);

    console.log(`Submitting transaction at: ${submissionTime.toISOString()}`);
    console.log(`Transaction hash: ${transaction.hash}`);

    await transaction.wait(0); // Make sure to set the confirmation count to 0

    console.log("Transaction confirmed");
    const confirmationTime = new Date();
    console.log(`Transaction confirmed at: ${confirmationTime.toISOString()}`);
    console.log(`Time difference: ${confirmationTime - submissionTime}ms`);
  }
You should see the confirmation time significantly lower than the standard RPC endpoint.

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Support

For feedback, support or questions about Flashblocks, please don’t hesitate to contact us in the #developer-chat channel in the Base Discord.