eth_newBlockFilter

eth_newBlockFilter creates a server-side filter on the Avalanche C-Chain (chain ID 43114, the EVM chain whose gas is paid in AVAX) that tracks new block arrivals. It returns a hex filter ID that you then poll with eth_getFilterChanges; each poll yields the hashes of blocks that have appeared since your last poll. With Snowman/Avalanche consensus finalizing blocks in roughly one to two seconds, new hashes show up quickly, so a tight polling loop keeps your app close to the chain head. Create the filter at https://avalanche.therpc.io/YOUR_API_KEY.

Use cases

• Trigger block-level processing each time a new C-Chain block arrives — for example re-checking pending transactions or settling positions on a perp protocol like GMX.
• Keep a cache fresh by invalidating derived data (balances, AVAX prices, pool reserves) on every new block hash the filter reports.

Parameters

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

Try it live in the Avalanche playground.

Errors & troubleshooting

Common pitfalls

• Polling returns only block hashes, not full blocks — fetch the contents you need separately with eth_getBlockByHash.
• Filters are dropped after a few minutes (around 5) without polling; if eth_getFilterChanges starts returning filter not found, recreate the filter and resume.
• Until a block is finalized it can in principle be replaced; the C-Chain's Snowman finality is fast (about 1–2 seconds), so prefer to act on blocks that have reached finality rather than the very latest hash.

Supported networks

• Mainnet — Chain ID: 43114
• Fuji

See also

• eth_getFilterChanges
• eth_uninstallFilter
• eth_newFilter
• eth_subscribe

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_newBlockFilter","params":[]}'