eth_subscribe on Avalanche
Everything below was measured on 2026-10-13 by calling eth_subscribe on Avalanche 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 Avalanche: what we measured
| newHeads | supported |
|---|---|
| First header after subscribing | 756 ms |
| Median gap between headers | 788 ms |
| Headers in 15 seconds | 17 |
| logs | supported |
| newPendingTransactions | supported |
What this means on Avalanche
Headers pushed over WebSocket are not identical to eth_getBlockByNumber over HTTP on Avalanche. Only the HTTP block has blockExtraData, size, totalDifficulty. 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/avalanche?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/avalanche?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 Avalanche
- 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_blockNot available
- trace_transactionNot available
eth_subscribe on other chains
- Ethereum
- Base
- Arbitrum
- Optimism
- Polygon
- BNB Smart Chain
- 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 Avalanche support eth_subscribe?
Yes. eth_subscribe answered on the SwiftNodes Avalanche endpoint when our weekly probe called it through the customer path (2026-10-13).
Does Avalanche support WebSocket subscriptions?
Yes. newHeads and logs worked through wss://rpc.swiftnodes.io/ws/avalanche on 2026-10-13.
Can I watch the Avalanche mempool?
newPendingTransactions is supported.
Avalanche endpoints, live block height and WebSocket status are on the Avalanche RPC page.
One key covers every chain we serve, and SwiftNodes has a free tier.