eth_newPendingTransactionFilter | Base

Base API method that creates a filter in the node to notify when new pending transactions are received. Chainstack Base reference.

POST /2fc1de7f08c0465f6a28e3c355e0cb14

eth_newPendingTransactionFilter

cURL

curl --request POST \
  --url https://base-mainnet.core.chainstack.com/2fc1de7f08c0465f6a28e3c355e0cb14 \
  --header 'Content-Type: application/json' \
  --data '
{
  "jsonrpc": "2.0",
  "method": "eth_newPendingTransactionFilter",
  "id": 1
}
'

import requests

url = "https://base-mainnet.core.chainstack.com/2fc1de7f08c0465f6a28e3c355e0cb14"

payload = {
    "jsonrpc": "2.0",
    "method": "eth_newPendingTransactionFilter",
    "id": 1
}
headers = {"Content-Type": "application/json"}

response = requests.post(url, json=payload, headers=headers)

print(response.text)

const options = {
  method: 'POST',
  headers: {'Content-Type': 'application/json'},
  body: JSON.stringify({jsonrpc: '2.0', method: 'eth_newPendingTransactionFilter', id: 1})
};

fetch('https://base-mainnet.core.chainstack.com/2fc1de7f08c0465f6a28e3c355e0cb14', options)
  .then(res => res.json())
  .then(res => console.log(res))
  .catch(err => console.error(err));

<?php

$curl = curl_init();

curl_setopt_array($curl, [
  CURLOPT_URL => "https://base-mainnet.core.chainstack.com/2fc1de7f08c0465f6a28e3c355e0cb14",
  CURLOPT_RETURNTRANSFER => true,
  CURLOPT_ENCODING => "",
  CURLOPT_MAXREDIRS => 10,
  CURLOPT_TIMEOUT => 30,
  CURLOPT_HTTP_VERSION => CURL_HTTP_VERSION_1_1,
  CURLOPT_CUSTOMREQUEST => "POST",
  CURLOPT_POSTFIELDS => json_encode([
    'jsonrpc' => '2.0',
    'method' => 'eth_newPendingTransactionFilter',
    'id' => 1
  ]),
  CURLOPT_HTTPHEADER => [
    "Content-Type: application/json"
  ],
]);

$response = curl_exec($curl);
$err = curl_error($curl);

curl_close($curl);

if ($err) {
  echo "cURL Error #:" . $err;
} else {
  echo $response;
}

package main

import (
	"fmt"
	"strings"
	"net/http"
	"io"
)

func main() {

	url := "https://base-mainnet.core.chainstack.com/2fc1de7f08c0465f6a28e3c355e0cb14"

	payload := strings.NewReader("{\n  \"jsonrpc\": \"2.0\",\n  \"method\": \"eth_newPendingTransactionFilter\",\n  \"id\": 1\n}")

	req, _ := http.NewRequest("POST", url, payload)

	req.Header.Add("Content-Type", "application/json")

	res, _ := http.DefaultClient.Do(req)

	defer res.Body.Close()
	body, _ := io.ReadAll(res.Body)

	fmt.Println(string(body))

}

HttpResponse<String> response = Unirest.post("https://base-mainnet.core.chainstack.com/2fc1de7f08c0465f6a28e3c355e0cb14")
  .header("Content-Type", "application/json")
  .body("{\n  \"jsonrpc\": \"2.0\",\n  \"method\": \"eth_newPendingTransactionFilter\",\n  \"id\": 1\n}")
  .asString();

require 'uri'
require 'net/http'

url = URI("https://base-mainnet.core.chainstack.com/2fc1de7f08c0465f6a28e3c355e0cb14")

http = Net::HTTP.new(url.host, url.port)
http.use_ssl = true

request = Net::HTTP::Post.new(url)
request["Content-Type"] = 'application/json'
request.body = "{\n  \"jsonrpc\": \"2.0\",\n  \"method\": \"eth_newPendingTransactionFilter\",\n  \"id\": 1\n}"

response = http.request(request)
puts response.read_body

200

{
  "jsonrpc": "<string>",
  "id": 123,
  "result": "<string>"
}

Base API method that creates a filter in the node to notify when new pending transactions are received. To check if the state has changed, call eth_getFilterChanges with the filter ID returned by this method.

On Base, this method returns an empty array by design — the mempool is private to the sequencer, so there are no public pending transactions to surface. For a real-time transaction stream, use Flashblocks instead.

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Parameters

• none

Response

• result — a string representing the filter ID. This ID should be used in subsequent calls to eth_getFilterChanges to retrieve new pending transactions.

Use case

The eth_newPendingTransactionFilter method is useful for applications that need to monitor the mempool for new transactions. Common use cases include:

• Building transaction monitoring tools
• Creating real-time transaction tracking interfaces
• Implementing MEV (Maximal Extractable Value) strategies
• Monitoring specific addresses for pending transactions

On Base, these patterns are not served by eth_newPendingTransactionFilter — the mempool is private to the sequencer, so the filter returns no pending transactions, and the eth_subscribe("newPendingTransactions") subscription stays empty too. The pending block tag returns pre-confirmed Flashblock state, not mempool contents, so a populated pending block does not mean this filter should return data. To stream transactions as the sequencer pre-confirms them, subscribe to eth_subscribe newFlashblockTransactions.

Note: After creating the filter, you need to poll eth_getFilterChanges periodically to get updates. Filters timeout if they’re not used for a period of time, so applications should be prepared to recreate them if necessary.

Body

application/json

jsonrpc · string · default: 2.0

method · string · default: eth_newPendingTransactionFilter

id · integer · default: 1

Response

200 - application/json

The ID of the created pending transaction filter

jsonrpc · string

id · integer

result · string