Ethereum Sepolia Testnet RPC Guide: How to Connect and Test (2026)

Sepolia is Ethereum’s recommended general-purpose testnet for smart contract development and dApp testing. It replaced Ropsten as the primary application developer testnet after the Merge and has been stable since. If you are building a dApp, DeFi protocol, NFT contract, or any EVM smart contract, Sepolia is where you test before mainnet.

This guide covers how to connect to Sepolia via RPC, which library to use, how to get test ETH, how to deploy and verify contracts. It also covers the most common issues development teams run into when running automated test suites against Sepolia.

For chain ID, MetaMask setup, endpoint format details, see the Ethereum Sepolia RPC endpoint page.

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What Sepolia Is For

Sepolia (chain ID: 11155111) is the go-to testnet for application-layer Ethereum development. It closely mirrors Ethereum mainnet in EVM behaviour, transaction lifecycle, JSON-RPC API surface. Smart contracts that pass testing on Sepolia behave as expected when deployed to mainnet.

Key use cases:

• Deploying and testing smart contracts before mainnet
• Running automated integration test suites against a live EVM chain
• Testing DeFi protocol interactions with real transaction flows
• Running dApp staging environments
• Validating event emission and log indexing with eth_getLogs
• CI/CD pipelines that run on every pull request

Sepolia’s validator set is permissioned and small, which keeps the chain stable and predictable. That is an advantage for application testing. For validator infrastructure or staking testing, use Hoodi testnet instead.

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Connecting to Sepolia Step by Step

Get your BoltRPC API key from trial.boltrpc.io. Replace YOUR_KEY with your actual key in the examples below.

HTTPS endpoint:

https://eu.endpoints.matrixed.link/rpc/ethereum-sepolia?auth=YOUR_KEY

WSS endpoint:

wss://eu.endpoints.matrixed.link/ws/ethereum-sepolia?auth=YOUR_KEY

ethers.js (v6)

import { ethers } from "ethers";

const provider = new ethers.JsonRpcProvider(
  "https://eu.endpoints.matrixed.link/rpc/ethereum-sepolia?auth=YOUR_KEY"
);

// Confirm chain ID (should be 11155111)
const network = await provider.getNetwork();
console.log("Chain ID:", network.chainId.toString()); // 11155111

const blockNumber = await provider.getBlockNumber();
console.log("Sepolia block:", blockNumber);

viem

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

const client = createPublicClient({
  chain: sepolia,
  transport: http(
    "https://eu.endpoints.matrixed.link/rpc/ethereum-sepolia?auth=YOUR_KEY"
  ),
});

const blockNumber = await client.getBlockNumber();
console.log("Block:", blockNumber);

Web3.py

from web3 import Web3

w3 = Web3(Web3.HTTPProvider(
    "https://eu.endpoints.matrixed.link/rpc/ethereum-sepolia?auth=YOUR_KEY"
))

print("Connected:", w3.is_connected())
print("Chain ID:", w3.eth.chain_id)   # 11155111
print("Block:", w3.eth.block_number)

curl

curl -X POST \
  "https://eu.endpoints.matrixed.link/rpc/ethereum-sepolia?auth=YOUR_KEY" \
  -H "Content-Type: application/json" \
  -d '{"jsonrpc":"2.0","method":"eth_blockNumber","params":[],"id":1}'

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Deploying Contracts to Sepolia

Hardhat

// hardhat.config.js
require("@nomicfoundation/hardhat-toolbox");

module.exports = {
  solidity: "0.8.24",
  networks: {
    sepolia: {
      url: "https://eu.endpoints.matrixed.link/rpc/ethereum-sepolia?auth=YOUR_KEY",
      chainId: 11155111,
      accounts: [process.env.SEPOLIA_PRIVATE_KEY],
    },
  },
};

npx hardhat run scripts/deploy.js --network sepolia

Foundry

# foundry.toml
[rpc_endpoints]
sepolia = "https://eu.endpoints.matrixed.link/rpc/ethereum-sepolia?auth=YOUR_KEY"

forge script script/Deploy.s.sol --rpc-url sepolia --broadcast

Deploy and verify in one script

import { ethers } from "ethers";

const provider = new ethers.JsonRpcProvider(
  "https://eu.endpoints.matrixed.link/rpc/ethereum-sepolia?auth=YOUR_KEY"
);
const wallet = new ethers.Wallet(process.env.PRIVATE_KEY, provider);

const factory = new ethers.ContractFactory(abi, bytecode, wallet);
const contract = await factory.deploy();
await contract.waitForDeployment();

const address = await contract.getAddress();
console.log("Deployed to Sepolia:", address);

// Verify deployment
const code = await provider.getCode(address);
console.log("Contract deployed:", code.length > 2);

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Getting Sepolia Test ETH

Test ETH on Sepolia has no real value. These are the current faucet options:

Sepolia Faucet (sepoliafaucet.com) URL: sepoliafaucet.com Requires a mainnet ETH balance to prevent abuse. Fast and reliable for development amounts.

Alchemy Sepolia Faucet URL: sepoliafaucet.com Requires account registration. Dispenses enough for most testing workflows.

pk910 Proof-of-Work Faucet URL: sepolia-faucet.pk910.de Browser-based proof-of-work. No social verification required. Slower but accessible without a mainnet balance.

For CI/CD pipelines and integration test suites that send many transactions, pre-fund a dedicated test wallet rather than relying on faucets per test run.

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Common Issues

Public RPC rate limits break test pipelines Public Sepolia endpoints impose request limits that are fine for manual testing but break under automated test suite load. Integration tests and CI/CD pipelines send bursts of requests. A dedicated endpoint handles this without throttling.

Wrong chain ID in MetaMask Sepolia’s chain ID is 11155111. If your wallet throws a network mismatch error, verify the chain ID is set correctly. ethers.js v6 detects it automatically; Hardhat config requires it explicitly.

eth_getLogs returns no events on recent blocks Sepolia blocks close approximately every 12 seconds. If you query logs immediately after sending a transaction, the block may not be confirmed yet. Add a confirmation wait before querying: await provider.waitForTransaction(txHash).

Nonce mismatch during parallel tests When test suites submit multiple transactions in parallel, nonce collisions can cause failures. Fetch the current nonce before each transaction: await provider.getTransactionCount(wallet.address, "pending").

Contract deployed but code returns 0x You queried eth_getCode before the deployment transaction confirmed. Wait for the receipt before calling getCode. The waitForDeployment() method in ethers.js handles this automatically.

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Useful Sepolia Methods

These are the methods most useful for development and testing workflows on Sepolia:

Method	Use
eth_blockNumber	Verify connectivity in test setup
eth_chainId	Confirm you are on Sepolia (returns 0x2A3F7 = 11155111)
eth_getBalance	Check test ETH in development wallets
eth_sendRawTransaction	Broadcast signed test transactions
eth_getTransactionReceipt	Confirm test transaction outcomes
eth_getLogs	Verify event emission after contract calls
eth_call	Run read-only contract tests without spending gas
eth_estimateGas	Estimate gas costs before deployment
eth_getCode	Confirm deployment was successful

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FAQ

What is the Ethereum Sepolia chain ID? Sepolia’s chain ID is 11155111. Set this in your wallet, Hardhat config, Foundry config, or any tool that requires a chain ID for network identification.

What is the Sepolia RPC URL with BoltRPC? The HTTPS endpoint is https://eu.endpoints.matrixed.link/rpc/ethereum-sepolia?auth=YOUR_KEY. Replace YOUR_KEY with your API key from trial.boltrpc.io.

Should I use Sepolia or Hoodi for testing? Use Sepolia for dApp development, smart contract testing, DeFi protocols, NFT contracts and any application-layer work. Use Hoodi if you are building validator infrastructure, testing deposit contracts or developing staking tooling.

How do I get test ETH for Sepolia? Use sepoliafaucet.com or sepolia-faucet.pk910.de. Test ETH has no real value. Most faucets require a mainnet ETH balance or social verification. For high-volume testing, pre-fund a wallet from a single faucet request rather than hitting faucets per test run.

Can I use the same API key for Sepolia and Ethereum mainnet? Yes. BoltRPC uses one API key across all networks. To switch from Sepolia to mainnet, change the slug from ethereum-sepolia to ethereum in the endpoint URL.

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Ready to connect to Sepolia with a reliable endpoint? Start your free 2-week trial at trial.boltrpc.io. Same API key format as Ethereum mainnet. No credit card required.