> ## Documentation Index
> Fetch the complete documentation index at: https://docs.chainstack.com/llms.txt
> Use this file to discover all available pages before exploring further.

# subscribe ("pendingTransactions") | Gnosis

> Reference docs for the subscribe ("pendingTransactions") JSON-RPC method on the Gnosis blockchain, available via Chainstack JSON-RPC nodes.

Gnosis Chain web3.js subscription equivalent to [eth\_newPendingTransactionFilter](/reference/gnosis-newpendingtransactionfilter). `subscribe("pendingTransactions")` allows developers to subscribe to real-time updates about new block headers on the gnosis blockchain; the application will receive notifications whenever a new block is added to the blockchain. The notification will include information about the new block, such as its block number, hash, and timestamp.

<Check>
  ### Get your own node endpoint today

  [Start for free](https://console.chainstack.com/) and get your app to production levels immediately. No credit card required.

  You can sign up with your GitHub, X, Google, or Microsoft account.
</Check>

## Parameters

* `string` — a keyword identifying the type of event to subscribe to, `pendingTransactions` in this case.
* `function` — (optional) a callback function that will be called every time a new event of the specified type is received. This function takes two parameters: `error` and `result`. The error parameter contains any error that occurred while subscribing to the event, and the result parameter contains the data for the event that was received.

## Response

* `string` — the hash identifying the pending transaction.

## `subscribe("pendingTransactions")` code example

<Info>
  Note that web3.js subscriptions require a WebSocket connection.
</Info>

Use the [event emitter instances](https://web3js.readthedocs.io/en/v1.2.11/web3-eth-subscribe.html#eth-subscription-return) to attach event listeners to the subscription object:

* `data` — activates for each new syncing event.
* `error` — activates if an error is detected during the subscription.
* `connected` — activates after the subscription is successfully connected and returns the subscription ID.
* `unsubscribe` — unsubscribes the subscription and returns `true` if successful.

<CodeGroup>
  ```javascript index.js theme={"system"}
  const Web3 = require("web3");
  const NODE_URL = "CHAINSTACK_WSS_URL";
  const web3 = new Web3(NODE_URL);

  async function subscribeToPendingTransactions() {
      try {
          // Create a new subscription to the 'pendingTransactions' event
          const subscription = await web3.eth.subscribe('pendingTransactions');

          // Attach event listeners to the subscription object
          subscription.on('connected', handleConnected);
          subscription.on('data', handleNewPending);
          subscription.on('error', handleError);
      } catch (error) {
          console.error(`Error subscribing to new pending transactions: ${error}`);
      }
  }

  /* Fallback functions to react to the different events */

  // Event listener that logs a message when the subscription is connected
  function handleConnected(subscriptionId) {
      console.log(`New subscription: ${subscriptionId}`);
  }

  // Event listener that logs the received pendingTransactions
  function handleNewPending(transactions) {
      console.log(transactions);
  }

  // Event listener that logs any errors that occur
  function handleError(error) {
      console.error(`Error receiving new blocks: ${error}`);
  }

  subscribeToPendingTransactions();
  ```
</CodeGroup>

## Use case

A practical use case for `subscribe("pendingTransactions")` is a DApp that continuously listens for new pending transactions, then isolates the `from`, `to`, and `value` fields for analytics purposes. This is useful, for example, to only track transactions that move at least a certain amount of xDAI.

The following is an implementation of this concept using web3.js subscriptions:

<CodeGroup>
  ```javascript index.js theme={"system"}
  const Web3 = require("web3");
  const NODE_URL = "CHAINSTACK_WSS_URL";
  const web3 = new Web3(NODE_URL);

  async function subscribeTopendingTransactions() {
      try {
          // Create a new subscription to the 'pendingTransactions' event
          const subscription = await web3.eth.subscribe('pendingTransactions');

          // Attach event listeners to the subscription object
          subscription.on('connected', handleConnected);
          subscription.on('data', handleNewPending);
          subscription.on('error', handleError);
      } catch (error) {
          console.error(`Error subscribing to new blocks: ${error}`);
      }
  }

  // Use this function to unsuscribe and exit the program
  function unsubscribe() {
      subscription.unsubscribe(function(error, success) {
          if (success) console.log("Successfully unsubscribed!");
          return process.exit(1)
      });
  }

  /* Fallback functions to react to the different events */

  // Event listener that logs a message when the subscription is connected
  function handleConnected(subscriptionId) {
      console.log(`New subscription: ${subscriptionId}`);
  }

  // Event listener that logs the received pendingTransactions and extracts from, to, and value fields
  async function handleNewPending(transactionHash) {
      try {
          const transaction = await web3.eth.getTransaction(transactionHash);
          const from = transaction.from;
          const to = transaction.to;
          const value = transaction.value;
          if (value >= 100000000000000000000) { // 100 xDAI in Wei
              console.log(`----- New pending transaction ------`);
              console.log(`From: ${from}`)
              console.log(`To: ${to}`)
              console.log(`Value: ${Number(web3.utils.fromWei(value, 'ether')).toFixed(2)} xDAI\n`)
          }
      } catch (error) {
          console.error(`Error getting transaction: ${error}`);
      }
  }

  // Event listener that logs any errors that occur
  function handleError(error) {
      console.error(`Error receiving new blocks: ${error}`);
  }

  subscribeTopendingTransactions();
  ```
</CodeGroup>

This code creates a new subscription to the `pendingTransactions` event using the `web3.eth.subscribe` method. This method returns a subscription object that can be used to attach event listeners to the subscription.

The code defines three event listener functions that are attached to the subscription object: `handleConnected`, `handleNewPending`, and `handleError`. The `handleConnected` function is called when the subscription is connected, and it logs a message with the subscription ID. The `handleNewPending` function is called when a new pending transaction is received; it runs the [eth\_getTransactionByHash](/reference/gnosis-gettransactionbyhash) method and extracts the `from`, `to`, and `value` fields. If the value transferred is above 100 xDAI, the data is logged.

The code includes the `unsuscribe` function that can be implemented in the logic to unsubscribe and exit the program when a condition is met.

The `handleError` function is called when an error occurs, and it logs an error message.

Finally, the code calls the `subscribeTopendingTransactions` function, which creates the subscription and attaches the event listeners. When a new pending transaction is received, the `handleNewPending` function is called to extract the data and log it to the console.