eth_getFilterChanges

eth_getFilterChanges returns everything that has matched a previously installed filter since you last polled it, so each call yields only the delta. What you get back depends on the filter type: a log filter returns log objects, a block filter returns new block hashes, and a pending-transaction filter returns transaction hashes. On Base — Coinbase's OP Stack rollup that settles to Ethereum L1 and meters gas in ETH — the ~2s sequencer cadence means new blocks and logs arrive quickly, so this is the lightweight way to keep a stream current. Send polls to https://base.therpc.io/YOUR_API_KEY (chain ID 8453, hex 0x2105); an empty array means nothing new since the last call.

Use cases

• Poll a log filter on a short interval (a couple of seconds suits Base's ~2s blocks) to pull new events without resending the address and topic criteria every time.
• Drive a block-tick loop: call eth_newBlockFilter once, then poll eth_getFilterChanges repeatedly to learn each new Base block hash as the sequencer seals it.

Parameters

Response

Example request

1curl https://base.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 Base playground.

Errors & troubleshooting

Common pitfalls

• Filters are dropped after about 5 minutes of inactivity; catch the filter not found error and recreate the filter rather than assuming it lives forever.
• On log filters always inspect the removed field — a Base block can be reorged before finalization, and removed: true marks a log that was rolled back.
• Tune the interval: hammering the endpoint burns CUs for empty deltas, while polling slower than the ~5-minute window risks the filter expiring between calls.

Supported networks

• Mainnet — Chain ID: 8453
• Sepolia — Chain ID: 84532

See also

• eth_newFilter
• eth_newBlockFilter
• eth_newPendingTransactionFilter
• eth_uninstallFilter

1curl https://base.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"]}'