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0.7.13 • Public • Published

Flashbots MEV-Share Client

Client library for MEV-Share written in Typescript.

Based on MEV-Share Spec.


Install from npm:

yarn add @flashbots/mev-share-client
# or
npm i @flashbots/mev-share-client

Alternatively, clone the library & build from source:

git clone https://github.com/flashbots/mev-share-client-ts
cd mev-share-client-ts
yarn install && yarn build
# in your project, assuming it has the same parent directory as mev-share-client-ts
yarn add ../mev-share-client-ts

use mev-share-client in your project

⚠️ Variables denoted in ALL_CAPS are placeholders; the code does not compile. examples/ contains compilable demos.

In your project:

import { Wallet, JsonRpcProvider } from "ethers"
import MevShareClient, {
} from "@flashbots/mev-share-client"

const provider = new JsonRpcProvider(RPC_URL)
const authSigner = new Wallet(FB_REPUTATION_PRIVATE_KEY, provider)

The MevShareClient class has built-in initializers for networks supported by Flashbots.

Connect to Ethereum Mainnet

const mevshare = MevShareClient.useEthereumMainnet(authSigner)

Connect to Ethereum Goerli

const mevshare = MevShareClient.useEthereumGoerli(authSigner)

Connect with an Ethers Provider or Chain ID

Networks supported by Flashbots have presets built-in. If it's more convenient, you can instantiate a MevShareClient using a chainId (or a ethers.js Network object, which has a chainId param).

import { JsonRpcProvider, Wallet } from "ethers" // ethers v6

/** connects to Flashbots MEV-Share node on goerli */
const provider = new JsonRpcProvider("http://localhost:8545", {chainId: 5, name: "goerli"})
const authSigner = new Wallet("0xac0974bec39a17e36ba4a6b4d238ff944bacb478cbed5efcae784d7bf4f2ff80")

const mevshare = MevShareClient.fromNetwork(authSigner, provider._network)

// manually with a chainId:
const mevshare = MevShareClient.fromNetwork(authSigner, {chainId: 5})

Connect to a custom network

To use custom network parameters, you can instantiate a new MevShareClient instance directly. This example is what the client uses to connect to mainnet:

const mevshare = new MevShareClient(authSigner, {
    name: "mainnet",
    chainId: 1,
    streamUrl: "https://mev-share.flashbots.net",
    apiUrl: "https://relay.flashbots.net"

See MevShareNetwork in src/api/interfaces for more details.


Source code

ℹ️ Examples require a .env file (or that you populate your environment directly with the appropriate variables).

cd src/examples
cp .env.example .env
vim .env

send a tx with hints

This example sends a transaction to the Flashbots MEV-Share node on Goerli from the account specified by SENDER_PRIVATE_KEY with a hex-encoded string as calldata.

yarn example.tx

backrun a pending tx

This example watches the mev-share streaming endpoint for pending mev-share transactions and attempts to backrun them all. The example runs until a backrun has been included on-chain.

yarn example.backrun

query event history

This example queries event history, starting from the beginning, until it finds events that share transactions and logs.

yarn example.history


See src/api/interfaces.ts for interface definitions.


Use on to start listening for events on mev-share. The function registers the provided callback to be called when a new event is detected.

const handler = mevshare.on("transaction", (tx: IPendingTransaction) => {
    // handle pending tx

// ... before terminating program


Sends a private transaction to the Flashbots MEV-Share node with specified hint parameters.

const wallet = new Wallet(PRIVATE_KEY)
const tx = {
    to: "0xfb000000387627910184cc42fc92995913806333",
    value: BigInt(1e13 * 275), // price of a beer if ETH is $2000
    data: "0x646f637320626179626565652121",
    gasLimit: 42000,
    maxFeePerGas: BigInt(1e9) * BigInt(42), // 42 gwei / gas
    maxPriorityFeePerGas: BigInt(1e9) * BigInt(2), // 2 gwei / gas
    chainId: 5,
    type: 2,

// privacy & inclusion settings
const shareTxParams: TransactionOptions = {
    hints: {
        logs: true,
        calldata: false,
        functionSelector: true,
        contractAddress: true,
    maxBlockNumber: undefined,
    builders: ["flashbots"]

const signedTx = await wallet.signTransaction(tx)
await mevshare.sendTransaction(SIGNED_TX, shareTxParams)


Sends a bundle; an array of transactions with parameters to specify conditions for inclusion and MEV kickbacks. Transactions are placed in the body parameter with wrappers to indicate whether they're a new signed transaction or a pending transaction from the event stream.

See MEV-Share Docs for detailed descriptions of these parameters.

const targetBlock = 1 + await provider.getBlockNumber()
const bundleParams: BundleParams = {
    inclusion: {
        block: targetBlock,
    body: [
        {hash: TX_HASH_FROM_EVENT_STREAM},
        {tx: SIGNED_TX, canRevert: false},
await mevshare.sendBundle(bundleParams)

Bundles that only contain signed transactions can share hints about the transactions in their bundle by setting the privacy parameter:

const targetBlock = 1 + await provider.getBlockNumber()
const bundleParams: BundleParams = {
    inclusion: {
        block: targetBlock,
        maxBlock: targetBlock + 5, // allow bundle to land in next 5 blocks
    body: [
        {tx: await wallet.signTransaction(TX1), canRevert: false},
        {tx: await wallet.signTransaction(TX2), canRevert: false},
    privacy: {
        hints: {
            txHash: true,
            calldata: true,
            logs: true,
            functionSelector: true,
            contractAddress: true,
const backrunResult = await mevshare.sendBundle(bundleParams)


Simulates a bundle. Accepts options to modify block header for simulation.

const bundle: BundleParams = {
    inclusion: {
        block: TARGET_BLOCK,
        maxBlock: TARGET_BLOCK + 3,
    body: [
        {hash: "0xTARGET_TX_HASH"},
        {tx: "0xSIGNED_BACKRUN_TX", canRevert: false}
    // ...

// ...
// assume you sent the bundle and it didn't land, and you want to see if it would have landed in the previous block, but need the tx to think it's in the target block

const simBundleOptions: SimBundleOptions = {
    parentBlock: TARGET_BLOCK - 1,
    blockNumber: TARGET_BLOCK,
    Set any of these (block header) fields to override their respective values in the simulation context: 
    // coinbase: string,
    // timestamp: number,
    // gasLimit: number,
    // baseFee: bigint,
    // timeout: number,

const simResult = await mevshare.simulateBundle(bundle, simBundleOptions)

This example uses the state of parentBlock, but overrides the state's blockNumber value. Setting more fields in SimBundleOptions is useful when testing smart contracts which have specific criteria that must be met, like the block being a certain number, or a specific timestamp having passed.


Get information about the event history endpoint for use in getEventHistory.


const info = await mevshare.getEventHistoryInfo()

returns something like this:

  count: 56934,
  minBlock: 9091377,
  maxBlock: 9190024,
  minTimestamp: 1685452445,
  maxTimestamp: 1686943324,
  maxLimit: 500


Get historical event stream data.

Using the data from our getEventHistoryInfo call, we can read events starting from the beginning. The data is paginated, so to read all of it, you'll have to make multiple calls to iterate through the it.

const info = await mevshare.getEventHistoryInfo()

// read every event
for (let i = 0; i < Math.ceil(info.count / info.maxLimit); i++) {
    const events = await mevshare.getEventHistory({
        limit: info.maxLimit,
        offset: i * info.maxLimit,
        blockStart: info.minBlock,

You can also filter events by timestamp:

const events = await mevshare.getEventHistory({
    limit: info.maxLimit,
    offset: i * info.maxLimit,
    timestampStart: 1686942023,




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