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eth_getFilterChanges

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`eth_getFilterChanges` is the polling half of the stateful filter API. You first create a filter — with [`eth_newBlockFilter`](eth_newBlockFilter.md) for new blocks or `eth_newFilter` for logs — and receive a filter ID. You then call `eth_getFilterChanges` with that ID, and the server returns the items that have appeared **since your previous call** (or since the filter was created, for the first poll). Each call advances the filter's cursor, so consecutive polls never return the same item twice.

This is the HTTP-based alternative to WebSocket subscriptions (`eth_subscribe`): instead of the server pushing updates to you, your client polls on an interval. On Polygon, where block time is roughly 2 seconds, a polling loop of about that interval keeps you close to the chain tip. The trade-off versus a WebSocket subscription is more requests and slightly higher latency, in exchange for working over plain request/response HTTP with no persistent connection.

The shape of the returned array depends on the **type** of filter the ID refers to: a block filter yields an array of 32-byte block hashes, while a log filter yields an array of log objects. A poll that finds nothing new returns an empty array — this is normal and not an error.

Filters are server-side resources with a limited lifetime. If a filter ID is unknown — never created, already removed with `eth_uninstallFilter`, or expired through inactivity — the call fails with `-32000 filter not found`. Treat that as a signal to recreate the filter and resume polling.

Parameters

This method takes no parameters.

Returns

eth_getFilterChanges return value
FieldType
resultobject

Examples

curl https://<your-endpoint>/ \
  -X POST -H 'Content-Type: application/json' \
  -d '{"jsonrpc":"2.0","id":1,"method":"eth_getFilterChanges","params":[]}'
const res = await fetch("https://<your-endpoint>/", {
  method: "POST",
  headers: { "Content-Type": "application/json" },
  body: JSON.stringify({
  "id": 1,
  "method": "eth_getFilterChanges",
  "params": [],
  "jsonrpc": "2.0"
}),
});
const data = await res.json();
import requests
resp = requests.post("https://<your-endpoint>/", json={"id":1,"method":"eth_getFilterChanges","params":[],"jsonrpc":"2.0"})
print(resp.json())

Usage

  1. Transport: HTTP (JSON-RPC).
  2. Networks: mainnet.
  3. Credit cost: 1 per call.

FAQ

What does eth_getFilterChanges do?
Polls a previously created server-side filter and returns everything that has matched since the last poll.
How many credits does eth_getFilterChanges cost?
eth_getFilterChanges costs 1 credit(s) per call on Triport by default.
Is eth_getFilterChanges available over WebSocket?
eth_getFilterChanges is an HTTP JSON-RPC method.