EVM transaction pool: pending vs queued

TLDR:

Pending transactions are in the pool ready to be included in a block.
Queued transactions are sitting locally because their account nonce is out of sequence; they don’t propagate until the gap is filled.
Inspect the pool with txpool_status / txpool_content; subscribe to new pending transactions with eth_subscribe; fix a queued transaction by filling the nonce gap.

Pending vs queued

A transaction submitted through an EVM node has one of two states before it lands in a block:

Pending — in the node’s transaction pool and ready to be included in the next block.
Queued — held in the local pool because the account nonce is out of sequence.

Each transaction has an account nonce (not the block nonce). The account nonce starts at 0 and must increase by one per transaction from that address. A transaction whose nonce is in sequence goes straight to pending. A transaction with a nonce gap waits in queued until the missing nonces are filled.

Example

Step	From	Nonce	State
1	`0x123...`	0	Pending → mined
2	`0x123...`	1	Pending → mined
3	`0x123...`	3	Queued (nonce 2 is missing)
4	`0x123...`	2	Pending → mined. Nonce 3 now moves to Pending and is mined too.

Inspect the local pool

Use the txpool JSON-RPC namespace to inspect the mempool of a node you have access to. On Chainstack, mempool access requires an Archive node with Debug and trace APIs enabled — see Mempool configurations for protocol-by-protocol availability.

curl YOUR_CHAINSTACK_ENDPOINT \
  -H 'content-type: application/json' \
  -d '{"jsonrpc":"2.0","method":"txpool_status","params":[],"id":1}'
# {"jsonrpc":"2.0","id":1,"result":{"pending":"0x4a","queued":"0x3"}}

curl YOUR_CHAINSTACK_ENDPOINT \
  -H 'content-type: application/json' \
  -d '{"jsonrpc":"2.0","method":"txpool_inspect","params":[],"id":1}'

curl YOUR_CHAINSTACK_ENDPOINT \
  -H 'content-type: application/json' \
  -d '{"jsonrpc":"2.0","method":"txpool_content","params":[],"id":1}'

To check the current confirmed nonce for an address:

curl YOUR_CHAINSTACK_ENDPOINT \
  -H 'content-type: application/json' \
  -d '{"jsonrpc":"2.0","method":"eth_getTransactionCount","params":["0xYourAddress","latest"],"id":1}'

For real-time delivery of new pending transactions, subscribe over WebSocket:

import asyncio
from web3 import AsyncWeb3, WebSocketProvider

WSS = "wss://ethereum-mainnet.core.chainstack.com/AUTH_KEY"

async def main():
    async with AsyncWeb3(WebSocketProvider(WSS)) as w3:
        subscription_id = await w3.eth.subscribe("newPendingTransactions")
        async for payload in w3.socket.process_subscriptions():
            print(payload["result"])  # transaction hash

asyncio.run(main())

wscat -c wss://ethereum-mainnet.core.chainstack.com/AUTH_KEY
> {"jsonrpc":"2.0","method":"eth_subscribe","params":["newPendingTransactions"],"id":1}

Each push notification over WebSocket counts as one request unit. For sustained high-volume pending-transaction subscriptions, consider an Unlimited Node which uses RPS-tiered flat-fee pricing instead of per-request billing.

HTTP-polling alternative

If you can’t use WebSocket, poll an HTTP filter with eth_newPendingTransactionFilter and eth_getFilterChanges:

curl YOUR_CHAINSTACK_ENDPOINT \
  -H 'content-type: application/json' \
  -d '{"jsonrpc":"2.0","method":"eth_newPendingTransactionFilter","params":[],"id":0}'
# {"jsonrpc":"2.0","id":0,"result":"0xb05a471a87c111bccadc9671f5b23b6a"}

curl YOUR_CHAINSTACK_ENDPOINT \
  -H 'content-type: application/json' \
  -d '{"jsonrpc":"2.0","method":"eth_getFilterChanges","params":["0xb05a471a87c111bccadc9671f5b23b6a"],"id":1}'

Filters expire after about five minutes of inactivity — see Fix Ethereum’s filter not found error.

Fix a queued transaction

If you have a queued transaction stuck behind a nonce gap, fill the gap by sending the missing nonces. The simplest path is to send no-op self-transfers at the missing nonces until the queued nonce becomes the next pending one.

Diagnose the gap

Get the confirmed nonce: eth_getTransactionCount("0xYourAddress","latest").
Get the queued transaction’s nonce from txpool_content or from the transaction object: eth_getTransactionByHash.
The gap is everything between them.

Fill the gap

Send a transaction at each missing nonce. A 0-value self-transfer with explicit nonce is enough:

from web3 import Web3

w3 = Web3(Web3.HTTPProvider("YOUR_CHAINSTACK_ENDPOINT"))
account = w3.eth.account.from_key("0xYOUR_PRIVATE_KEY")
confirmed = w3.eth.get_transaction_count(account.address, "latest")
stuck_nonce = 12  # nonce of your queued transaction

for nonce in range(confirmed, stuck_nonce):
    tx = {
        "from": account.address,
        "to":   account.address,
        "value": 0,
        "nonce": nonce,
        "gas":   21000,
        "maxFeePerGas":         w3.to_wei(50, "gwei"),
        "maxPriorityFeePerGas": w3.to_wei(2,  "gwei"),
        "chainId": w3.eth.chain_id,
    }
    signed = account.sign_transaction(tx)
    w3.eth.send_raw_transaction(signed.raw_transaction)

Once the missing nonces confirm, the previously queued transaction moves to pending and is mined.

Alternative: cancel by replacement

If you’d rather drop the queued transaction altogether, send a replacement at the same nonce with a higher gas price — most clients require the new gas price to be at least 10% higher (txpool.pricebump).

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EVM transaction pool: pending vs queued

Pending vs queued

Example

Inspect the local pool

HTTP-polling alternative

Fix a queued transaction

Diagnose the gap

Fill the gap

Alternative: cancel by replacement

See also

​Pending vs queued

​Example

​Inspect the local pool

​Subscribe to new pending transactions

​HTTP-polling alternative

​Fix a queued transaction

​Diagnose the gap

​Fill the gap

​Alternative: cancel by replacement

​See also

Pending vs queued

Example

Inspect the local pool

Subscribe to new pending transactions

HTTP-polling alternative

Fix a queued transaction

Diagnose the gap

Fill the gap

Alternative: cancel by replacement

See also