Once the smart contract is deployed on the blockchain the code cannot be changed anymore. If developers can’t update the code, they can’t fix bugs. To solve this problem, Ethereum protocol developers set up alternative networks solely for testing smart contracts.
What is Sepolia testnet and how to start using it – in this brief guide.
What is Sepolia: Introduction
Ethereum provides an environment where developers can deploy and test Solidity contracts and interactions with them in the same way they would on the mainnet. Specifically designed for this purpose, Sepolia mirrors the Ethereum blockchain structure and components but with some differences that allow safe testing and experimentation.
Sepolia meaning
To put it briefly, Sepolia can be defined as a test network or a sandbox environment separate from the mainnet (main network) but closely imitating its functioning. In order to understand what is Sepolia ETH, let’s first check out the lifespan of Ethereum testnets.
N.B.: Refer to our mainnet vs test networks guide for a more detailed comparison.
It is currently one of the two stable and well-maintained testing environments in Ethereum.
What is Sepolia ETH?
Test Ether is a token used on the test network. It performs the same set of functions ‘real’ ETH is designed for, however, it has no real-world value or price. They can be easily retrieved via ether faucets, which supply free test tokens.
What is Sepolia Testnet?
Testnets are a crucial part of the development lifecycle for Ethereum and EVM-based projects, allowing for thorough testing before any code goes live on the mainnet.
Here’s a brief overview of how Sepolia can be used:
- deploy decentralized applications and identify code vulnerabilities;
- check how applications interact with other services;
- test the implementation of token standards, such as ERC-20 or ERC-721;
- check how different transaction types are processed;
With that, the main use case of this test network is pre-launching applications, contracts, and tooling in a realistic blockchain environment but without involving real assets.
What is Sepolia Ethereum?
Operational since 2021, Sepolia functions as a center and default public test network for the Ethereum ecosystem.
Layer 2 testnets are closely integrated with it. This ensures that developers can build their applications in an environment that closely resembles the real-world interactions between Layer 1 and Layer 2 (L2).
What is Sepolia Base?
The testnet specifically designed for Base, an Ethereum L2 network, is known as Base Sepolia. Since Q1 2024, it is the core test network for Base after the deprecation of Base Goerli.
Developers use this environment to practice building and launching their smart contracts and dApps, ensuring the code is error-free when they move to the mainnet.
What is Sepolia Arbitrum?
Arbitrum is a Layer 2 solution for Ethereum, known for its optimistic rollup technology, which provides significant scalability benefits.
Arbitrum offers a testnet platfrom specifically tailored for developers to test products, services, and smart contracts built on the L2 chain. Test ETH used for this purpose can be requested for free from an Arbitrum faucet.
The Difference Between Sepolia and Other Testnets
Goerli and Holesky are other latest public test environments for Ethereum, yet, designed for different purposes. Here’s a brief comparison of Ethereum testnets in their post-merge state:
| Sepolia | Holesky | Goerli (deprecated) | |
|---|---|---|---|
| Chain ID | 11155111 | 17000 | 5 |
| Consensus | PoA (closed validator set) | PoS (open to public validators) | PoS (permissionless) |
| Purpose | Building and testing smart contracts and dApps | Testing protocol upgrades and staking mechanism | Simulate staking operations |
| Key features | Stability, long-term support | Long-term support | No longer maintained |
By separating the roles, Ethereum's ecosystem ensures that specific types of testing and development are conducted in the most appropriate and efficient environments.
Sepolia vs Goerli vs Holesky
Goerli had been around for five years before it was retired in March 2024 and stopped receiving protocol upgrades. Goerli served as more of a validator network for testing staking setups. This created an issue of scarcity for Goerli ETH.
Holesky was launched in September 2023 to replace the Goerli testnet. Holesky is similarly intended to allow testing staking therefore anyone can become a validator and participate in its consensus.
In contrast, Sepolia is intended for application testing. Plus, the test Ether is readily available via various ETH faucets so developers can get as many free tokens as possible for all their needs. In general, for developers needing to practice application deployments, it is the testnet of choice.
How to Use Sepolia Testnet?
Using the test network only requires two simple steps:
- Retrieving an RPC URL to connect to the network;
- Funding the wallet with test tokens.
To create a free personal RPC link, developers can register on GetBlock and use this URL to connect to the Ethereum testnet.
This URL can be used to add the test network to MetaMask:
Here’s an example of how to use the URL with web3.js library:
const { Web3 } = require('web3');
const web3 = new Web3('https://go.getblock.io/');
To perform transactions and interact with smart contracts on testnet, developers need test tokens. They can be easily deposited directly to the developer's wallet from the faucet. Try GetBlock’s testnet faucet to receive 0.1 test Ether instantly.
With this setting, users can start sending requests to the testnet, perform transactions, and experiment with Solidity contracts.
What is Sepolia Test Network: Summary
Tetsnets are realistic blockchain environments mainly used by developers. Sepolia is where they can test and experiment with their Ethereum applications, ensuring they are well-prepared for deployment on the mainnet.
It is designed and maintained by core protocol developers to be freely and easily accessible. Anyone who has testnet tokens can start using this test network.
