Mempool API

Connect to Blocknative transaction monitoring services directly with webhooks

Overview

This documentation describes how to connect to and use Blocknative's transaction monitoring service using webhooks. The service delivers near real time notifications of Ethereum transaction state changes via POSTs to your URL (webhook). Each state change is a JSON payload with all the transaction details.

To use our API with web sockets, please see the SDK.

API usage has rate limits. Please see Rate Limits for more details.

Getting Started

Setup API Key

1. Create a Blocknative account by clicking the Sign up button on Mempool Explorer and following the instructions. Account creation requires email confirmation to complete.

2. Blocknative will create a Default API key for your account that you can use. You can create additional API keys from your account page on explorer.blocknative.com/account by clicking the Add new API key button to the upper right.

3. Secret keys additionally are available to be generated for API keys which allow secure usage of configuration modification endpoints.

Add new API key button

API Key creation form

Setup Webhook

Create a new webhook for an API key by clicking the "Add a Webhook" button to the right of the API key. This will reveal a form to enter the webhook specifics: URL, blockchain (currently Ethereum and Bitcoin are supported), and network. See below for Supported Networks. You can optionally include a username and password if your webhook used basic authentication.

Webhook creation form

We support Slack webhooks. If you want to create a Discord webhook, append /slack to the end of the Discord URL to use its Slack compatibility mode.

Slack webhooks must begin with https://hooks.slack.com/services. Discord webhooks must begin with https://discordapp.com/api/webhooks.

Slack and Discord limit the size of messages so notifications involving large contract inputs may be abbreviated. Normal, i.e. not Slack/Discord, webhooks are not abbreviated.

Add Address to Watch

Add an address to watch by clicking the Watch Address button and entering the address.

Ethereum addresses begin with a 0x followed by 40 characters (hexadecimal). Any valid Ethereum address can be used, including external accounts and smart contracts. The following Bitcoin addresses are valid:

Watch Address form

To stop notifications for an address, use the View Address button next to Add webhook, and click the Delete icon next to the address you'd like to stop watching.

View Addresses button lets you view a list of all addresses you're watching on that API Key

It is safe to add the same address multiple times or to unwatch addresses not being watched.

Authentication

No authentication is currently required to facilitate testing, apart from configuration modification endpoints. Basic auth (username/password) is supported and recommended for production use, and we are adding additional authentication methods based on customer requirements. We recommend HTTPS requests but also offer support for HTTP.

Secret keys

Secret keys are available to be generated per API key, which can be used to access these endpoints:

• ****Get all configuration scopes

• ****Get configuration in specific scope

• ****Add a configuration

• ****Delete a configuration

These end points require a 'credentials' header which takes the API key and associated secret key in one variable in the form "apiKey:secretKey".

Example: 9ed49579-a78b-4c82-b796-6db3aded6ed2:67ed12d1-f0ab-4f18-812c-58356684728b

Screencasts

See how to setup a Slack webhook in this screencast:

How to Setup a Webhook Screencast

API

Add transaction to watch

POST https://api.blocknative.com/transaction

Use the Blocknative https://api.blocknative.com/transaction endpoint to

POST

individual transaction hashes to watch for state changes (mempool and chain confirmation). For each transaction, specify your API key, the transaction

hash

or

txid

to watch, the transaction's blockchain (currently

ethereum

and

bitcoin

are supported), and the network to watch (see supported networks below).

Request Body

Name	Type	Description
	string	JSON payload: \ { \ "apiKey": "<api-key>", \ "hash": "<transaction-hash (ethereum)>", \ "txid": "<txid (bitcoin)>" \ "blockchain": "ethereum", \ "network": "main" \ }

200

{
    "msg": "success"
}

400

Response body will describe nature of request failure.

Examples:
XYZ is not a valid apiKey
(string `hash` or `txid`) XYZ is an invalid transaction hash / txid
(string `blockchain`) XYZ is not supported
(string `network`) XYZ is an invalid network

apiKey is the API Key created from Setup API Key step above. hash is the transaction hash to watch. (ethereum only) blockchain is the blockchain system to monitor. ethereum is supported at this time. network is the Blockchain network to monitor for the specified transaction hash. See below for Supported Networks.

Example curl call:

Ethereum

curl -X POST -H "Content-Type: application/json" -d '{"apiKey":"<api-key>","hash":"<transaction-hash>","blockchain":"ethereum","network": "main"}' https://api.blocknative.com/transaction 

Remove transaction to watch

DELETE https://api.blocknative.com/transaction

Use the Blocknative https://api.blocknative.com/transaction endpoint to DELETE individual transaction hashes that you are currently watching. For each transaction, specify your API key, the transaction hash or txid to watch, the transaction's blockchain (currently ethereum and bitcoin are supported), and the network to watch (see supported networks below).

Request Body

Name	Type	Description
	String	JSON payload: \ { \ "apiKey": "<api-key>", \ "hash": "<transaction-hash (ethereum)>", \ "txid": "<txid (bitcoin)>" \ "blockchain": "ethereum", \ "network": "main" \ }

200: OK

{
    // Response
}

400: Bad Request

{
    // Response
}

Add address to watch

POST https://api.blocknative.com/address

Use the Blocknative https://api.blocknative.com/address endpoint to

POST

individual addresses to watch for transactions. For each address, specify your API key, the address to watch, the blockchain (currently Ethereum and Bitcoin are supported), and the networks to watch (see supported networks below).

\

Request Body

Name	Type	Description
	string	JSON payload: \ { \ "apiKey": "<api-key>", \ "address": "<account-address>", \ "blockchain": "ethereum", \ "networks": "main" \ }

200

{
    "msg": "success"
}

400

Response body will describe nature of request failure.

Examples:
XYZ is not a valid apiKey
(string `address`) XYZ is an invalid ethereum address
(string `blockchain`) XYZ is not supported
(array `networks`) ["XYZ"] contains an invalid network

apiKey is the API Key created from Setup API Key step above. address is the external account address to watch. blockchain is the blockchain system to monitor. ethereum is supported at this time. networks is an array containing 1 or more networks to monitor for the specific address. See below for Supported Networks.

Example curl call:

Ethereum

curl -X POST -H "Content-Type: application/json" -d '{"apiKey":"<api-key>","address":"<account-address>","blockchain":"ethereum","networks":["main"]}' https://api.blocknative.com/address 

This endpoint will return success if the specified address on the specified network(s) are already being watched for the apikey.

Remove address to watch

DELETE https://api.blocknative.com/address

Use the Blocknative https://api.blocknative.com/address endpoint to

DELETE

individual addresses from watching for transactions. For each address, specify your API key, the address to remove, the blockchain (currently

ethereum

and

bitcoin

are supported), and the networks to remove from watch (see supported networks below).

Request Body

Name	Type	Description
	string	JSON payload: \ { \ "apiKey": "<api-key>", \ "address": "<account-address>", \ "blockchain": "ethereum", \ "networks": ["main", "rinkeby"] \ }

200

{
    "msg": "success"
}

400

Response body will describe nature of request failure.

Examples:
XYZ is not a valid apiKey
(string `address`) XYZ is an invalid ethereum address
(string `blockchain`) XYZ is not supported
(array `networks`) ["XYZ"] contains an invalid network

apiKey is the API Key created from Setup API Key step above. address is the external account address to remove from watching. blockchain is the blockchain for the address. ethereum is supported at this time. networks is an array containing 1 or more networks to remove monitoring for the specific address. See below for Supported Networks.

Example curl call:

Ethereum

curl -X DELETE -H "Content-Type: application/json" -d '{"apiKey":"<api-key>","address":"<account-address>","blockchain":"ethereum","networks":["main"]}' https://api.blocknative.com/address 

This endpoint will return success if the specified address on the specified network(s) was not being watched for the apikey.

List of watched addresses

GET https://api.blocknative.com/address/<your-api-key>/<blockchain>/<network>/

Use this endpoint to access the watched addresses for your API key. Include your API key and the appropriate blockchain (currently

ethereum

and

bitcoin

are supported) and network. See below for Supported Networks.

Path Parameters

Name	Type	Description
your-api-key	string	Your API key
blockchain	string	Blockchain with watched addresses
network	string	Network with watched addresses

Query Parameters

Name	Type	Description
page	number	The page of watched addresses to receive
size	number	The size of a page
order	string	The creation time order of watched addresses

200

{
    "total": 0, // total number of watched addresses
    "page": 1, // current page number of watched addresses
    "pageSize": 1000, // maximum size of current page
    "items": [] // array of watched address strings
}

400

Response body will describe nature of request failure.

Examples:
XYZ is not a valid apiKey

Required elements of the API request path

your-api-key is the API Key created from Setup API Key step above. blockchain is the blockchain for the watched addresses you want to retrieve. ethereum is supported. network is the network for the watched addresses you want to retrieve. See below for Supported Networks.

Optional query string parameters for large lists

page is the page number, of multiple pages, you want to retrieve. Use the total value in the API response along with the size parameter to iterate over all the pages of watched addresses. size is the length of a page of results. The default size is 100 items per page. The maximum size is 1000 items per page. order is the sort of the retrieved items according to when they were added to the list (via POST described earlier). The sort order must be either asc (oldest - newest) or desc (newest to oldest). Default is asc.

API requests are rate limited. Use larger page sizes for larger lists in order to get all items.

List of watched transactions

GET https://api.blocknative.com/transaction/<your-api-key>/<blockchain>/<network>/

Use this endpoint to access the watched transactions for your API key. Include your API key and the appropriate blockchain (currently

ethereum

and

bitcoin

are supported) and network. See below for Supported Networks.

Path Parameters

Name	Type	Description
your-api-key	string	Your API key
blockchain	string	Blockchain with watched transactions
network	string	Network with watched transactions

Query Parameters

Name	Type	Description
page	number	The page of watched transactions to receive
size	number	The size of a page
order	string	The creation time order of watched transactions

200

{
    "total": 0, // total number of watched transactions
    "page": 1, // current page number of watched transactions
    "pageSize": 1000, // maximum size of current page
    "items": [] // array of watched transaction hash/id strings
}

400

Response body will describe nature of request failure.

Examples:
XYZ is not a valid apiKey

Required elements of the API request path

your-api-key is the API Key created from Setup API Key step above. blockchain is the blockchain for the watched transactions you want to retrieve. ethereum is supported. network is the network for the watched transactions you want to retrieve. See below for Supported Networks.

Optional query string parameters for large lists

page is the page number, of multiple pages, you want to retrieve. Use the total value in the API response along with the size parameter to iterate over all the pages of watched transactions. size is the length of a page of results. The default size is 100 items per page. The maximum size is 1000 items per page. order is the sort of the retrieved items according to when they were added to the list (via POST described earlier). The sort order must be either asc (oldest - newest) or desc (newest to oldest). Default is asc.

API requests are rate limited. Use larger page sizes for larger lists in order to get all items.

Get all configuration scopes

GET https://api.blocknative.com/<blockchain>/<network>/configs

Use this endpoint to access all of the configuration scopes given on an API key. Include the appropriate blockchain and network, for which supported networks are listed below. Include your API key and it's associated secret key in a "credentials" header via the formatting "apiKey:secretKey". Your secret key can be set via your Accounts page where your keys are listed.

Path Parameters

Name	Type	Description
network	string	Network with watched addresses
blockchain	string	Blockchain with watched addresses

Headers

Name	Type	Description
credentials	string	Here we define an API key and secret key together in the form "apiKey:secretKey"

200

[
    "global",
    "0x7a250d5630b4cf539739df2c5dacb4c659f2488d"
]

400

Response body will describe nature of request failure.

Examples:
incorrect or no header apiKey:secretKey given
XYZ is not a valid apiKey
invalid secret key

Get configuration in specific scope

GET https://api.blocknative.com/<blockchain>/<network>/configs/<raw-scope>

Use this endpoint to access the full config deployed at a specific blockchain, network, API key and scope. Include the appropriate blockchain and network, for which supported networks are listed below. Include your API key and it's associated secret key in a "credentials" header via the formatting "apiKey:secretKey". Your secret key can be set via your Accounts page where your keys are listed.

Path Parameters

Name	Type	Description
raw-scope	string	The desired scope, options for this path can be retrieved by the 'Get all configuration scope' endpoint detailed above
network	string	Network with watched addresses
blockchain	string	Blockchain with watched addresses

Headers

Name	Type	Description
credentials	string	Here we define an API key and secret key together in the form "apiKey:secretKey"

200

{
    "configName": "example config name",
    "fields": [
        "example field"
    ],
    "filters": [
        {
            "status": "example"
        }
    ],
    "abi": []
}

400

Response body will describe nature of request failure.

Examples:
incorrect or no header apiKey:secretKey given
XYZ is not a valid apiKey
invalid secret key

Add a configuration

PUT https://api.blocknative.com/<blockchain>/<network>/configs/<raw-scope>

Use this endpoint to add configurations to certain API keys at certain blockchains and networks. Include your API key and it's associated secret key in a "credentials" header via the formatting "apiKey:secretKey".

\

\

Configurations can be exported from Mempool Explorer as specified here (https://docs.blocknative.com/mempool-explorer#configurations-sidebar).

Path Parameters

Name	Type	Description
raw-scope	string	The desired scope, options for this path can be retrieved by the 'Get all configuration scope endpoint' detailed above
network	string	Network with watched addresses
blockchain	string	Blockchain with watched addresses

Headers

Name	Type	Description
credentials	string	Here we define an API key and secret key together in the form "apiKey:secretKey"

Request Body

Name	Type	Description
	string	Example JSON payload for an address: \ { \ "configName": "example", \ "fields": ["example field"], \ "filters": [{"status": "pending"}], \ "abi" : [] \ }

200

{
    "msg": "ok"
}

400

Response body will describe nature of request failure.

Examples:
incorrect or no header apiKey:secretKey given
XYZ is not a valid apiKey
invalid secret key
Cannot set config item <key> in <scope>
Reached max config limit for <apiKey>:<blockchain>:<network>

There is a limit of 50 configurations per API key. If you need to watch more than 50 addresses and also filter them, it is recommended that you subscribe to all of the addresses and then use a 'global' scoped filter that will apply to all of those addresses.

Websocket configuration example

{
    "configName": "Limiting my public BN API key",
    "allowedOrigins": ["http://example.com", "http://example2.com"],
    "ipNotificationRatelimit": 250,
    "ipNotificationRatelimitWindow": 1,
    "ipPendingSimulationRatelimit": 50,
    "ipPendingSimulationRatelimitWindow": 1
}

Global configuration example

{
    "configName": "Global config example",
    "fields": ["example field"],
    "filters": [{"status": "pending"}]
}

Address configuration example

{ 
    "configName": "Example address config",
    "fields": ["example field"],
    "filters": [{"status": "pending"}],
    "abi" : []
}

Delete a configuration

DELETE https://api.blocknative.com/<blockchain>/<network>/configs/<raw-scope>

Using this endpoint, you can clear a configuration set at a certain API key for a blockchain, network and scope. Include your API key and it's associated secret key in a "credentials" header in the form "apiKey:secretKey".

Path Parameters

Name	Type	Description
raw-scope	string	The desired scope, options for this path can be retrieved by the 'Get all configuration scope endpoint' detailed above
network	string	Network with watched addresses
blockchain	string	Blockchain with watched addresses

Headers

Name	Type	Description
credentials	string	Here we define an API key and secret key together in the form "apiKey:secretKey"

200

{
    "msg": "ok"
}

400

Response body will describe nature of request failure.

Examples:
incorrect or no header apiKey:secretKey given
XYZ is not a valid apiKey
invalid secret key

Ethereum Notifications

Transaction state changes are POSTed to your custom URL (webhook) with a JSON payload containing the transaction details. The contents of the payload depends on the type of transactions.

Base Payload

The following fields are included in every transaction notification and are captured directly from the mempool or block data. Fields are not ordered.

  "from": String,
  "to": String,
  "nonce": Number,
  "gas": Number,
  "gasPrice": String,
  "gasPriceGwei": Number,
  "gasUsed": Number, present only when the tx is on-chain,
  "baseFeePerGas": String,
  "baseFeePerGasGwei": Number,
  "maxPriorityFeePerGas": String,
  "maxPriorityFeePerGasGwei": Number,
  "maxFeePerGas" String,
  "maxFeePerGasGwei" Number,
  "type": Number,
  "value": String,
  "hash": String,
  "input": String,
  "v": String,
  "r": String,
  "s": String,
  "blockHash": String, or null when status is 'pending',
  "blockNumber": String, or null when status is 'pending',
  "estimatedBlocksUntilConfirmed": Number, or null for estimates of 1-5

Field	Description
from	The address initiating, signing, the transaction
to	Address receiving the transaction
nonce	The from address nonce (transaction count from that address)
gas	Maximum amount of gas available to the transaction
gasUsed	Gas used during transaction execution. Only present when the tx is on-chain.
value	Amount of ETH transferred directly from from address
hash	Transaction id hash unique for every transaction
input	Data sent to transaction. For direct value transfers from one external account to another, this field contains 0x. For contract calls, this value contains the contract method signature and params as a hex string.
v	Transaction signature component (hex encoded)
r	Transaction signature component (hex encoded)
s	Transaction signature component (hex encoded)
blockHash	Block id hash for transactions that are on-chain. Field is null unless notification status is confirmed or failed
blockNumber	Block number for transactions that are on-chain. Field is null unless notification status is confirmed or failed
estimatedBlocksUntilConfirmed	Predicted number of blocks from pendingBlockNumberuntil confirmation based ongasPriceand Gas Platform data. Field is 1 - 5 or nullfor estimates outside of 1 - 5.
type	Denotes the gas pricing used for this transaction.

Gas Details

Notifications include gas price information depending on the type of the transaction.

For an in-depth look at how EIP-1559 transactions are priced, see:

A Definitive Guide to Ethereum EIP-1559 Gas Fee Calculations

Type 2 (EIP-1559) Transactions

Field	Description
baseFeePerGas	Base fee per gas of this block
maxPriorityFeePerGas	Max priority fee per gas in wei
maxFeePerGas	Max fee per gas in wei
baseFeePerGasGwei	baseFeePerGas in gwei, rounded to the 3rd most significant digit
maxPriorityFeePerGasGwei	maxPriorityFeePerGas in gwei, rounded to an integer
maxFeePerGasGwei	maxFeePerGas in gwei, rounded to an integer

Type 0 (Pre-EIP-1559) Transactions

Field	Description
gasPrice	Amount, in wei, per unit of gas
gasPriceGwei	Amount, in gwei, per unit of gas, rounded to an integer

Metadata Payload

In addition to the transaction details provided from the mempool or block, the JSON payload is augmented with the following field. Fields are not ordered.

  "system": String,
  "network": String,
  "status": Status,
  "apiKey": String,
  "monitorVersion": String,
  "monitorId": String,
  "serverVersion": String,
  "timeStamp": String, // the UTC time of first detection of current status
  "pendingTimeStamp": String // ISO UTC time of initial pending status detection
  "pendingBlockNumber": Number // the chain head block number at time of pending detection
  "transactionIndex": Number, // optional, present if status confirmed, failed
  "blockTimeStamp": String, // optional, present if status confirmed, failed - UTC time of miner block creation
  "timePending": String, // optional, present if status confirmed, failed, speedup, cancel. "-1" if first detectiong is on-chain.
  "blocksPending": Number, // optional, present if status confirmed, failed, speedup, cancel
  "asset": String, // optional, present if direct transfer of ETH or ERC20
  "direction": String, // optional, present in payloads with a `watchedAddress` param
  "counterparty": String, // optional, present in payloads with a `watchedAddress` param
  "watchedAddress": String, // optional, present when payload triggered by activity related to a watched address
  "replaceHash": String, // optional, present if status is speedup or cancel
  "failureReason": String, // optional, present if status is failed

Field	Description
system	Blockchain of this transaction
network	Network name of this transaction (see table to supported networks below)
status	New status of this transaction (see table of supported status values below)
apiKey	Blocknative API key associated with the notification
monitorVersion	Version number of the Blocknative monitor that detected the transaction state change
monitorId	Identifier of the Blocknative monitor that first detected the transaction state change
serverVersion	Version number of the Blocknative server that delivered the notification
timeStamp	UTC ISO timestamp when Blocknative first detected this transaction update
pendingTimeStamp	UTC ISO timestamp when Blocknative first detected the pending state for this transaction
pendingBlockNumber	The chain head block number when the pending state was first detected
transactionIndex	Optional. For confirmed or failed transactions, the index (order) of the transaction in the block.
blockTimeStamp	Optional. **** UTC ISO block timestamp the miner reported when collating the block this transaction was eventually confirmed in. The block timestamp is usually a few seconds before timeStamp, the difference being the time between the validator collating the block, and the block being confirmed and propagated throughout the network
timePending	Optional. The number of milliseconds from initial pending detection to confirmed or failed detection. "-1" if first detection is on-chain.
blocksPending	Optional. The number of blocks since the initial pending detection to confirmed or failed detection.
asset	Optional. Symbol of the asset being transferred, e.g. ETH. This field is present only if transaction directly transfers Ether or is an ERC20 token transfer
direction	Optional. Indicates if funds are incoming or outgoing relative to the watchedAddress. This field is present only if notification triggered by watchedAddress
counterparty	Optional. Address of recipient of funds if watchedAddress is the sender in the transaction, address of sender of funds if watchedAddress is the recipient in the transaction. This field is present only if notification triggered by watchedAddress
watchedAddress	Optional. Watched address which triggered the notification. This field is present only if notification triggered by watchedAddress
replaceHash	Optional. The hash of the transaction that replaced this transaction in the txpool
failureReason	Optional. For failed transactions, the reason why the transaction failed. Some failures may not have a discernible reason.

Decoded Contract Payload

For some contract calls, Blocknative decodes the input field of the transaction to interpret details of the contract method call. Fields are not ordered.

  "contractCall": {
    "contractType": String,
    "contractAddress": String,
    "methodName": String,
    "params": {
      // key value pairs specific to the contract method
    },
    "contractName": String,
    "contractDecimals": Number (optional),
    "decimalValue": String (optional),
  }

Blocknative currently supports decoding of the following contracts and regularly adds more:

• Uniswap v3 (Mainnet and Matic)

• Uniswap Universal Router (Mainnet and Matic)

• Uniswap v2 (Routing and Factory - Mainnet and Matic)

• Uniswap v1 (Mainnet and Matic)

• Sushiswap Router

• 0x Protocol v2.1

• 0x Protocol v3

• Curve.Fi (All pools shown here)

• Synthetix ExchangeRates

• Synthetix Proxy

• MakerDAO

• Rebalancing Set Exchange Issuance v2

• Set Protocol

• Abridged

• Pillar Badge

• rToken

• 1inch Exchange V1

• 1inch Exchange V2

• 1inch Exchange V3

• Aave: Lending Pool V2

• Aave Flashloans

• OpenSea

• Balancer (BFactory, BPool, Distribution and Exchange Proxy 2)

• Honeyswap Router (Gnosis Chain)

• Sushiswap V2 Factory

• DIGG Orchestrator

• Quickswap Router & Factory (Matic)

• Aave Lending Pool (Matic)

• Aavegotchi: Opensea (Matic)

• ERC 4337 EntryPoints

Along with supported Ethereum token protocols:

• ERC-20

• ERC-721

• ERC-165

• ERC-777

• ERC-1820

Field	Description
contractType	Type of the called contract
contractAddress	Address of the called contract
methodName	Name of the called method
params	Optional. A series of keys and values specific to the contract method. This field is present only if the contract method call includes parameters.
contractName	Optional. **** Name of the called contract
contractDecimals	Optional. The result of calling the decimal() method on the smart contract, if it exists
decimalValue	Optional. If there is a value field in the params object, and contractDecimals is present, decimalValue will equal value / 10^contractDecimals

Internal Transactions Payload

Blocknative will send confirmednotifications when a watchedAddress is detected in the internal transactions of a contract call. In this case, the confirmed notification will include details of the internal transactions and balance changes resulting from those internal transactions. Fields are not ordered.

"internalTransactions": [],
"netBalanceChanges": Object

Field	Description
internalTransactions	Array of objects containing details of each internal transaction (see below)
netBalanceChanges	Object containing details of balance changes for all addresses involved in internal transactions (see below)

The internalTransactions array contains details on each internal transaction executed by the contract call of the parent (main) transaction. Fields are not ordered.

"internalTransactions": [
  {      
    "type": String,
    "from": String,
    "to": String,
    "input": String,
    "gas": Number,
    "gasUsed": Number,
    "value": String,
    "contractCall": Object (optional, contains an additional param 'contractAlias' which will be the symbol of the token if this is an erc20 transfer or transferFrom)
  },
  ...
]

Field	Description
type	Type of internal transaction (one of CALL, DELEGATECALL, STATICCALL, CALLCODE)
from	Address initiating the internal transaction call (typically the parent (main) transaction's contract address
to	Address the internal transaction is calling or sending value to
input	Data sent to internal transaction. For value transfers from external account initiating parent (main) transaction to another external account, this field contains 0x. For contract calls, this value contains the contract method signature and params as a hex string.
gas	Maximum amount of gas available to the internal transaction
gasUsed	Amount of gas actually used executing the internal transaction
value	Amount of ETH transferred directly to to address from parent (main) transaction from address.
contractCall	Optional. A series of keys and values specific to the contract method . This object is present only if the contract method call includes parameters and Blocknative decodes the internal transaction contract call (e.g. an ERC20 transfer). For details see decoded contract payload above. NOTE: If the Internal transaction is an ERC20 transfer or transferFrom call, the contractCall object will include an additional field, contractAlias with the symbol of the token transferred.

The netBalanceChanges object contains details of all the balance changes resulting from the internal transactions details in the internalTransactions array. The object is an array with an entry for each address involved in the internal transactions.

"netBalanceChanges": [
  {
    "address": String,
    "balanceChanges": [
      {
        "delta": String,
        "asset": {
          "contractAddress": String
          "symbol": String,
          "type": String
        },
        "breakdown": [
          {
            "amount": String,
            "counterparty": String
          },
          ...
        ]
      }
    ]
  },
  ...
]

Field	Description
address	Address involved in internal transaction. Each address contains an array of balances changes, one for each counterparty
delta	Amount of value transfer (balance change) in wei to theaddress. Outgoing value is represented as a negative balance change and incoming value is represented as a positive balance change
asset	Details of the asset being transferred. Contains contractAddress, type and symbol
contractAddress	The address of the token contract if the value is not ETH (ether), not present if the value os ETH
type	The type of asset transferred (e.g. "ether" or "erc20")
symbol	The symbol of the asset transferred. "ETH" or appropriate ERC20 symbol
breakdown	Array of individual transfers to address for the current asset
counterparty	Address of the other side of the transfer relative to the address
amount	The amount of asset transferred with this counterparty

Simulated Pending Payload

Blocknative will send pending-simulationnotifications when a watchedAddress is detected in the from or to field of the main transaction or internal transactions of a contract call. The notification will include details of the internal transactions and balance changes resulting from those internal transactions. The internal transaction details and balance changes are probabilistic based on simulating the transaction against the latest confirmed block. Fields are not ordered.

pending-simulation notifications are only available for Ethereum Mainnet and Sepolia Testnet.

The payload structure for pending-simulation notifications is the same as for confirmed notifications with the addition of the following object.

"simDetails": {
    "blockNumber": Number,
    "performanceProfile": {
      "breakdown": [
        {
          "label": "detected",
          "timeStamp": String // UTC time of first detection of transaction
        },
        {
          "label": "traceStart",
          "timeStamp": String // UTC time of when transaction simulation started
        },
        {
          "label": "traceEnd",
          "timeStamp": String // UTC time of when transaction simulation completed
        },
        {
          "label": "dispatch",
          "timeStamp": String // UTC time of when notification sent
        }
      ],
      "e2eMs": Number // end to end processing time in milliseconds
    }
  }

Examples

Direct send transaction

A direct send transaction is sending funds (ether) from one account to another. The hash is setup as a watched transaction and/or to address or the from addresses or both are setup as watched addresses.

{
  "system": "ethereum",
  "nonce": 1061,
  "id": "6f782dbf-248f-c46f-9a56-c53794f1",
  "network": "rinkeby",
  "from": "0x6f782dbf141c50e0b79b044b471fb8d76bcb7aed",
  "status": "pending",
  "blockHash": "0x0000000000000000000000000000000000000000000000000000000000000000",
  "blockNumber": null,
  "gas": 21000,
  "gasPrice": "10000000000",
  "gasPriceGwei": 10,
  "hash": "0x7fb386cc248fc46f9a56c53794f1580b6c48f6e16e4c2c5ed5e7a533af2ac2cf",
  "input": "0x",
  "to": "0x87c382487b6f20926acf7076de1210845d62e7cc",
  "transactionIndex": 0,
  "value": "100000000000000000",
  "asset": "ETH",
  "direction": "outgoing",
  "counterparty": "0x87c382487b6f20926acf7076de1210845d62e7cc",
  "watchedAddress": "0x6f782dbf141c50e0b79b044b471fb8d76bcb7aed",
  "apiKey": "3462c0f0-471f-4b7d-84c3-50e0244a9403"
}

As a direct ETH transfer, this transaction has 0x for its input.

Contract call transaction

When watched transaction is a contract call, or a watched address makes a contract call, a similar transaction notification is generated where the to address is the contract.

{
  "system": "ethereum",
  "nonce": 1066,
  "id": "e08fc37a-db98-4954-be23-757719c7317c",
  "from": "0x6F782dBf141C50E0B79b044B471FB8D76Bcb7aeD",
  "network": "rinkeby",
  "status": "confirmed",
  "blockHash": "0xcef0fe0ce003662287777425181006e141ae517793e148e856076c6ae50c1023",
  "blockNumber": 4862011,
  "gas": 36402,
  "gasPrice": "1000000000",
  "gasPriceGwei": 1,
  "hash": "0x1ae540c5f8e4f50e951a3192d05cfd2da1028d4c7275455087de6dddd1139188",
  "input": "0x6c5c7a700000000000000000000000006921144ad2a2923ae11c5652feb3b0d9053d9152",
  "to": "0x9E7aE8c4D07670Df36FdB88c1b3Ae06dc4625fa0",
  "transactionIndex": 6,
  "value": "0",
  "asset": "ETH",
  "direction": "outgoing",
  "counterparty": "0x9E7aE8c4D07670Df36FdB88c1b3Ae06dc4625fa0",
  "watchedAddress": "0x6f782dbf141c50e0b79b044b471fb8d76bcb7aed",
  "apiKey": "15273e72873dba2cd065"
}

As a contract call, this transaction has a value for input. The value contains the contract method signature and and parameters to the method call.

If you would like to have your contract decoded (method and parameter names delivered in JSON message) please contact Blocknative at [e-mail] or on our Discord server with your contract address (for each supported network) and ABI.

Token transfer transaction

If the watched transaction is a ERC-20/ERC-721 transfer, or an ERC-20/ERC-721 token transfer or transferFromtransaction involves a watched address, the details of the transfer and token involved are included in the transaction notification.

{
    "system": "ethereum",
    "nonce": 67,
    "from": "0x87c382487b6f20926acf7076de1210845d62e7cc",
    "network": "rinkeby",
    "id": "87c38248-acd2-5d28-cc9a-b7e0eb72",
    "status": "pending",
    "blockHash": "0x0000000000000000000000000000000000000000000000000000000000000000",
    "blockNumber": null,
    "gas": 54643,
    "gasPrice": "10000000000",
    "gasPriceGwei": 10,
    "hash": "0xb85704efacd25d28cc9ab7e0eb726a30ed4dd4607a5008d57eb69bc262db503f",
    "input": "0xa9059cbb0000000000000000000000006f782dbf141c50e0b79b044b471fb8d76bcb7aed0000000000000000000000000000000000000000000000004563918244f40000",
    "to": "0xaff4481d10270f50f203e0763e2597776068cbc5",
    "transactionIndex": 0,
    "value": "5000000000000000000",
    "asset": "WEENUS",
    "contractCall": {
        "contractType": "erc20",
        "contractAddress": "0xaff4481d10270f50f203e0763e2597776068cbc5",
        "methodName": "transfer",
        "params": {
            "_to": "0x6f782dbf141c50e0b79b044b471fb8d76bcb7aed",
            "_value": "5000000000000000000"
        }
    },
    "direction": "outgoing",
    "counterparty": "0x6f782dbf141c50e0b79b044b471fb8d76bcb7aed",
    "watchedAddress": "0x87c382487b6f20926acf7076de1210845d62e7cc",
    "apiKey": "15273e72873dba2cd065"
}

Supported Networks

Ethereum and EVM Compatible

Name	Id	Description
main	1	Ethereum Mainnet
sepolia	11155111	Ethereum Testnet
xdai	100	Gnosis Chain
matic-main	137	Polygon
matic-mumbai	80001	Polygon Testnet

Transaction Events (State Changes)

Key	Description
pending	the transaction was detected in the "pending" area of the mempool and is eligible for inclusion in a block
pending-simulation	the transaction was detected in the "pending" area of the mempool and is eligible for inclusion in a block and has been simulated against the latest block
stuck	the transaction was detected in the "queued" area of the mempool and is not eligible for inclusion in a block
speedup	a replacement transaction (same nonce and from, higher gas) was detected in the mempool with the same to, value and input parameters as the transaction being replaced
cancel	a replacement transaction (same nonce and from, higher gas) was detected in the mempool with different to, value or input parameters compared to the transaction being replaced
confirmed	the transaction was mined or validated with no errors
failed	the transaction was mined or validated, but failed to execute due to EVM error
dropped	the transaction was dropped from the mempool before being mined or validated into a block

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