eth_newFilter

eth_newFilter registers a server-side log filter — defined by an address, a block range, and topic criteria — and returns a hex filter ID. You poll that ID with eth_getFilterChanges to pull only the logs that matched since your last poll, without resending the full filter each time. On Polygon, the MATIC-powered PoS chain at https://polygon.therpc.io/YOUR_API_KEY (chain ID 137, 0x89), this is the standard way to follow contract events over plain HTTP — handy for tracking activity on busy DeFi venues like QuickSwap or Aave.

Use cases

• Poll for new ERC-20 Transfer events — for instance from the Polygon USDT contract at 0xc2132D05D31c914a87C6611C10748AEb04B58e8F — on a short interval without re-specifying the full filter each round.
• Monitor a QuickSwap pair contract for Swap events from a long-running indexer or bot, letting the server track your position in the log stream between polls.

Parameters

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_newFilter",
7    "params": [{}],
8    "id": 1
9  }'

Try it live in the Polygon playground.

Errors & troubleshooting

Common pitfalls

• A filter is discarded after roughly five minutes of inactivity; handle the filter not found error from eth_getFilterChanges by recreating the filter and resuming from a known block.
• Server-side filter state is scoped to the connection and lost on reconnect or node failover, so always keep the original filter definition and be ready to re-register it.
• For real-time event streams on Polygon's ~2-second cadence, an eth_subscribe log subscription over WebSocket pushes matches to you and is more efficient than repeatedly polling a filter.

Supported networks

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

See also

• eth_getFilterChanges
• eth_getFilterLogs
• eth_uninstallFilter
• eth_getLogs

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_newFilter","params":[]}'