eth_subscribe on Arbitrum
Everything below was measured on 2026-10-13 by calling eth_subscribe on Arbitrum 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 Arbitrum: what we measured
| newHeads | supported |
|---|---|
| First header after subscribing | 283 ms |
| Median gap between headers | 262 ms |
| Headers in 15 seconds | 54 |
| logs | supported |
| newPendingTransactions | supported |
What this means on Arbitrum
Headers pushed over WebSocket are not identical to eth_getBlockByNumber over HTTP on Arbitrum. Only the HTTP block has l1BlockNumber, sendCount, sendRoot, size. Fetch the block over HTTP if you need those fields.
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/arbitrum?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/arbitrum?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 Arbitrum
- 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_transactionNot available
eth_subscribe on other chains
- Ethereum
- Base
- 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 Arbitrum support eth_subscribe?
Yes. eth_subscribe answered on the SwiftNodes Arbitrum endpoint when our weekly probe called it through the customer path (2026-10-13).
Does Arbitrum support WebSocket subscriptions?
Yes. newHeads and logs worked through wss://rpc.swiftnodes.io/ws/arbitrum on 2026-10-13.
Can I watch the Arbitrum mempool?
newPendingTransactions is supported.
Arbitrum endpoints, live block height and WebSocket status are on the Arbitrum RPC page.
One key covers every chain we serve, and SwiftNodes has a free tier.