How to Write a Smart Contract in Solidity (2025 Tutorial)

Frequently Asked Questions

01.What version of Solidity should I use in 2025?

Use a recent 0.8.x release: 0.8.26 or later was current in May 2025. The 0.8 line introduced built-in overflow checks and custom errors. Always pin your pragma (e.g. `pragma solidity 0.8.26;`) rather than using a floating caret for production contracts.

02.Is Remix IDE still a good starting point for Solidity development?

Yes. Remix (remix.ethereum.org) remains the fastest zero-install way to write, compile, and deploy Solidity. It includes the Solidity compiler, a JavaScript VM for local testing, MetaMask injection for testnet deploys, and a built-in static analyzer. Most developers graduate to Foundry or Hardhat for larger projects.

03.Do I need to pay gas to test a smart contract?

No. Remix's JavaScript VM simulates deployments with zero cost. For testnet deploys on Sepolia or Holesky you need testnet ETH from a faucet, which is free. Real gas costs apply only on Ethereum mainnet or other live L1/L2 networks.

04.What is the difference between memory, storage, and calldata in Solidity?

`storage` is persistent on-chain state and costs the most gas to modify. `memory` is a temporary in-function buffer, cleared after the call. `calldata` is a read-only area holding function arguments for external calls: it is the cheapest and should be preferred for external function parameters that are not mutated.

05.Should I write my own ERC-20 or use OpenZeppelin?

Use OpenZeppelin Contracts for anything going to production. Its ERC-20 implementation is audited, battle-tested, and covers edge cases (return values, allowance race conditions) that a hand-rolled token usually misses. Writing your own ERC-20 is a valuable learning exercise but a liability in production.