eth_newPendingTransactionFilter

eth_newPendingTransactionFilter creates a server-side filter on Arbitrum One for incoming pending transactions and returns a hex filter ID. Polling that ID with eth_getFilterChanges yields the hashes of transactions that have entered the node's pending set since your last poll. On Arbitrum One — the ETH-fee Optimistic Rollup on Nitro/ArbOS — a single sequencer orders transactions rather than a public peer-to-peer mempool, so the pending window is brief: the sequencer's sub-second soft confirmations mean a transaction usually moves from pending to mined very quickly. The endpoint is https://arbitrum.therpc.io/YOUR_API_KEY (chain ID 42161, 0xa4b1).

Use cases

• Watch the pending set for transactions from a specific sender on Arbitrum One, fetching each hash's full transaction to filter by from and react before it is mined.
• Build a fee tracker by sampling the gas parameters of pending transactions to gauge what tip and max fee the sequencer is currently seeing.

Parameters

This method takes no parameters. Pass an empty array [].

Response

Example request

1curl https://arbitrum.therpc.io/YOUR_API_KEY \
2  -X POST \
3  -H "Content-Type: application/json" \
4  -d '{
5    "jsonrpc": "2.0",
6    "method": "eth_newPendingTransactionFilter",
7    "params": [],
8    "id": 1
9  }'

Try it live in the Arbitrum One playground.

Errors & troubleshooting

Common pitfalls

• Polling returns only transaction hashes — call eth_getTransactionByHash for each one to read sender, value, and gas fields.
• A pending transaction may never be mined or may be replaced by a higher-fee transaction with the same nonce, so never treat a pending hash as confirmed; poll eth_getTransactionReceipt to confirm inclusion.
• During heavy load the sequencer's pending set can flood your polls with many hashes at once; for real-time consumption on Arbitrum One prefer eth_subscribe over WebSocket instead of repeated polling.

Supported networks

• Mainnet — Chain ID: 42161
• Sepolia — Chain ID: 421614

See also

• eth_getFilterChanges
• eth_uninstallFilter
• eth_newFilter
• eth_subscribe

1curl https://arbitrum.therpc.io/YOUR_API_KEY \
2  -X POST \
3  -H 'Content-Type: application/json' \
4  -d '{"jsonrpc":"2.0","id":1,"method":"eth_newPendingTransactionFilter","params":[]}'