Arbitrum Sepolia RPC Endpoint

Chain ID 421614. Arbitrum One's testnet: Nitro, about 4 blocks a second, settling to Ethereum Sepolia.

Online right now, checked every 2 minutes. WebSocket: available.

Endpoints

https://rpc.swiftnodes.io/rpc/arbitrum-sepolia?key=YOUR_API_KEY
wss://rpc.swiftnodes.io/ws/arbitrum-sepolia?key=YOUR_API_KEY

The same API key works here and on Arbitrum mainnet, and testnet requests count toward your plan like any other request. The free plan includes testnets. Going to mainnet means changing arbitrum-sepolia to arbitrum in the URL.

import { createPublicClient, http } from "viem";
import { arbitrumSepolia } from "viem/chains";

const client = createPublicClient({
  chain: arbitrumSepolia,
  transport: http("https://rpc.swiftnodes.io/rpc/arbitrum-sepolia?key=YOUR_API_KEY"),
});

console.log(await client.getBlockNumber());

About Arbitrum Sepolia

Arbitrum Sepolia is the testnet for Arbitrum One. It runs the same Nitro software, produces blocks only when there are transactions (about four a second when we measured), and settles to Ethereum Sepolia.

Because blocks are so frequent, block-number arithmetic written for Ethereum goes wrong quickly: 1,000 blocks here is about four minutes. Page eth_getLogs by result count as well as block range, since the upstream we measured refuses queries that match more than 10,000 logs.

What we measured

Measured through our endpoint on October 18, 2026.

Chain ID	421614 (0x66eee)
Client	nitro v3.12.2
Block 1	August 22, 2023
Block interval	0.26 s average over 200 blocks
eth_gasPrice	0.02 gwei
eth_getLogs	1,000 unfiltered blocks returned 34,914 logs; 10,000 blocks hit "logs matched by query exceeds limit of 10000"
safe / finalized	2,028 and 3,890 blocks behind the head

Frequently asked questions

What is the Arbitrum Sepolia chain ID?

421614, or 0x66eee in hex.

Is the Arbitrum Sepolia RPC endpoint free?

Yes. The free plan covers Arbitrum Sepolia at 20 requests per second and 250,000 requests a month, on the same key as Arbitrum One.

Why did my eth_getLogs query fail on Arbitrum Sepolia?

The query matched too many logs. With blocks every quarter second, 10,000 unfiltered blocks returned more than the 10,000-log limit. Filter by address and topics, or use smaller ranges.

Does Arbitrum Sepolia support the finalized tag?

Yes. Finalized follows the Sepolia L1 block that contains the batch. When we measured it was 3,890 blocks behind the head.

Other testnets

Get a free Arbitrum Sepolia endpoint

One key for every testnet and mainnet we serve. No credit card, no KYC.

Get your API key