eth_subscribe

eth_subscribe opens a push-based subscription over a WebSocket connection to a Base node, so the node streams notifications the moment events occur instead of forcing you to poll on a timer. Base is Coinbase's OP Stack optimistic rollup that settles to Ethereum L1 and pays gas in ETH, and its sequencer produces a fresh block roughly every two seconds — fast enough that polling wastes calls and still misses updates between requests. With one open socket you can subscribe to newHeads, contract logs, newPendingTransactions, or syncing and let those ~2-second blocks arrive as eth_subscription events. Connect to https://base.therpc.io/YOUR_API_KEY (chain ID 8453, hex 0x2105) over its WebSocket transport to start a stream.

Use cases

• Stream newHeads to drive real-time Base dashboards — each ~2-second block header arrives over the socket, so block-height counters and gas widgets update without polling.
• Receive live logs from a Base contract as they are mined, for example Aerodrome or Uniswap swap events, by passing an address/topics filter and reacting to each emission instantly.
• Monitor newPendingTransactions to watch hashes enter the Base sequencer's mempool, useful for tracking a user's submitted ETH transfer before it lands on chain.

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_subscribe",
7    "params": [
8        "newHeads",
9        {}
10      ],
11    "id": 1
12  }'

Try it live in the Base playground.

Errors & troubleshooting

Common pitfalls

• eth_subscribe only works over a WebSocket connection. Calling it over the plain HTTP endpoint returns a "notifications not supported" error — point your client at the Base WebSocket transport, not the request/response HTTP URL.
• Events emitted while the socket is down are gone for good. Add reconnect logic, and after reconnecting backfill the gap with eth_getLogs over the missed Base block range so no swaps or transfers are dropped.
• During an L1-driven reorg, logs notifications can include entries with removed: true. Handle these explicitly and roll back the affected state rather than treating every event as final.

Supported networks

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

See also

• eth_unsubscribe
• eth_newFilter
• eth_getLogs
• eth_getFilterChanges

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_subscribe","params":["",null]}'