eth_newPendingTransactionFilter

eth_newPendingTransactionFilter creates a server-side filter that captures transactions entering the mempool and returns a hex filter ID. Polling that ID with eth_getFilterChanges yields the hashes of pending transactions seen since your last poll. On Polygon — the MATIC-fueled PoS chain at https://polygon.therpc.io/YOUR_API_KEY (chain ID 137, 0x89) — this gives an HTTP client a window into unconfirmed activity before blocks seal roughly every two seconds, useful for mempool monitoring and gas-price sampling.

Use cases

• Watch the Polygon mempool for pending transactions and, after fetching each by hash, flag those from a sender or to a contract you care about — for example incoming USDT transfers at 0xc2132D05D31c914a87C6611C10748AEb04B58e8F.
• Build a live gas-price tracker by sampling the maxPriorityFeePerGas and maxFeePerGas of pending transactions, giving users a real-time read on what tip is clearing on Polygon right now.

Parameters

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Response

Example request

1curl https://polygon.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 Polygon playground.

Errors & troubleshooting

Common pitfalls

• The poll returns only transaction hashes — call eth_getTransactionByHash for each one when you need the sender, value, or fee fields.
• A pending transaction may never be mined, may be dropped, or may be replaced by one with the same nonce and a higher fee; never treat a hash from this filter as a confirmed MATIC transaction.
• During Polygon congestion the mempool can be large, so a single poll may return thousands of hashes; for sustained real-time monitoring an eth_subscribe (newPendingTransactions) stream over WebSocket scales better than polling.

Supported networks

• Mainnet — Chain ID: 137
• Amoy — Chain ID: 80002

See also

• eth_getFilterChanges
• eth_uninstallFilter
• eth_newFilter
• eth_subscribe

1curl https://polygon.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":[]}'