eth_subscribe on Base
Everything below was measured on 2026-10-13 by calling eth_subscribe on Base through the same endpoint customers use, and is re-measured weekly.
What eth_subscribe does
Opens a subscription over WebSocket: newHeads pushes each new block header, logs pushes matching events, and newPendingTransactions pushes mempool transaction hashes where the node exposes them. It replaces polling, and it only works over WebSocket, not HTTP.
eth_subscribe on Base: what we measured
| newHeads | supported |
|---|---|
| First header after subscribing | 341 ms |
| Median gap between headers | 2.0 s |
| Headers in 15 seconds | 8 |
| logs | supported |
| newPendingTransactions | not supported: Unsupported subscription: newPendingTransactions |
What this means on Base
Headers pushed over WebSocket are not identical to eth_getBlockByNumber over HTTP on Base. Only the HTTP block has withdrawals. Fetch the block over HTTP if you need those fields.
newPendingTransactions is not available, so mempool watching on Base is not possible through this endpoint. Rollups with a single sequencer have no public mempool to stream.
Subscriptions end when the connection drops. Reconnect with backoff and, after reconnecting, fetch the blocks you missed with eth_getBlockByNumber.
Example request
wscat -c "wss://rpc.swiftnodes.io/ws/base?key=YOUR_API_KEY"
> {"jsonrpc":"2.0","id":1,"method":"eth_subscribe","params":["newHeads"]}import { createPublicClient, webSocket } from "viem";
const client = createPublicClient({
transport: webSocket("wss://rpc.swiftnodes.io/ws/base?key=YOUR_API_KEY", { reconnect: true }),
});
const unwatch = client.watchBlocks({
onBlock: (block) => console.log(block.number, block.hash),
});
// Events from one contract, pushed as they are mined
client.watchContractEvent({ address: token, abi: erc20Abi, eventName: "Transfer", onLogs: (logs) => console.log(logs) });Other methods on Base
- eth_blockNumberSupported
- eth_chainIdSupported
- eth_getBalanceSupported
- eth_getBlockByNumberSupported
- eth_getTransactionByHashSupported
- eth_getTransactionReceiptSupported
- eth_callSupported
- eth_estimateGasSupported
- eth_gasPriceSupported
- eth_maxPriorityFeePerGasSupported
- eth_sendRawTransactionSupported
- eth_getTransactionCountSupported
- eth_getCodeSupported
- eth_getLogsSupported
- eth_getBlockReceiptsSupported
- eth_feeHistorySupported
- eth_getProofSupported
- eth_createAccessListSupported
- debug_traceCallSupported
- trace_blockSupported
- trace_transactionSupported
eth_subscribe on other chains
- Ethereum
- Arbitrum
- Optimism
- Polygon
- BNB Smart Chain
- Avalanche
- Sonic
- Linea
- Scroll
- zkSync Era
- Blast
- Mantle
- Gnosis
- Celo
- Berachain
- Monad
- Unichain
- Kaia
- PulseChain
- World Chain
- Ronin
- Abstract
- ApeChain
- MegaETH
- Fantom
- Lisk
- Hemi
- X Layer
- BOB
- Plasma
- Fraxtal
- Zora
- Story
- Soneium
- Sei
- Hyperliquid
- Taiko
- Morph
- Ink
- Katana
- Ethereum Classic
- opBNB
- Mode
- Flare
- Core
- Chiliz
- Telos EVM
- Tempo
- Cronos
- Manta Pacific
- Shibarium
- Boba Network
- Arbitrum Nova
- Immutable zkEVM
Frequently asked questions
Does Base support eth_subscribe?
Yes. eth_subscribe answered on the SwiftNodes Base endpoint when our weekly probe called it through the customer path (2026-10-13).
Does Base support WebSocket subscriptions?
Yes. newHeads and logs worked through wss://rpc.swiftnodes.io/ws/base on 2026-10-13.
Can I watch the Base mempool?
No: newPendingTransactions is not available.
Base endpoints, live block height and WebSocket status are on the Base RPC page.
One key covers every chain we serve, and SwiftNodes has a free tier.