eth_getFilterChanges

eth_getFilterChanges returns everything that matched a previously installed filter since your last call, so you poll for fresh activity on the Avalanche C-Chain without re-sending the filter criteria each time. What you get back depends on the filter type: log objects for a log filter, block hashes for a block filter, or transaction hashes for a pending-transaction filter. The C-Chain settles transactions (paid for in AVAX) under Snowman consensus with roughly 1–2 second finality, so the windows between polls are short. Call it against https://avalanche.therpc.io/YOUR_API_KEY (chain ID 43114, 0xa86a) using the filter ID you got at creation time.

Use cases

• Poll on a short interval (a couple of seconds suits the C-Chain's fast block cadence) for new log events without re-specifying address or topic filters on every request.
• Drive a block-tick loop: create one block filter with eth_newBlockFilter, then poll eth_getFilterChanges repeatedly to react to each new Avalanche block as it finalizes.

Parameters

Response

Example request

1curl https://avalanche.therpc.io/YOUR_API_KEY \
2  -X POST \
3  -H "Content-Type: application/json" \
4  -d '{
5    "jsonrpc": "2.0",
6    "method": "eth_getFilterChanges",
7    "params": ["0x1"],
8    "id": 1
9  }'

Try it live in the Avalanche playground.

Errors & troubleshooting

Common pitfalls

• Filters expire after roughly 5 minutes of inactivity; catch the filter not found error and recreate the filter rather than assuming the ID stays valid forever.
• For log filters, check each log's removed field — a short reorg can mark previously delivered C-Chain logs as removed even with fast finality.
• Polling too aggressively burns compute units; polling too rarely risks letting the filter expire — pick an interval that tracks the C-Chain's sub-2-second blocks without idling past the timeout.

Supported networks

• Mainnet — Chain ID: 43114
• Fuji

See also

• eth_newFilter
• eth_newBlockFilter
• eth_newPendingTransactionFilter
• eth_uninstallFilter

1curl https://avalanche.therpc.io/YOUR_API_KEY \
2  -X POST \
3  -H 'Content-Type: application/json' \
4  -d '{"jsonrpc":"2.0","id":1,"method":"eth_getFilterChanges","params":["0x1"]}'