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<\/figure>\n\n\n\nA smart contract is a program stored on a blockchain that runs exactly as written when its conditions are met. Once it’s deployed, no one \u2014 including its author \u2014 can quietly change the logic, and anyone on the network can call it.<\/p>\n\n\n\n
That permanence is the real difference from a normal app. A web server can be edited or switched off by whoever owns it; a deployed contract keeps running on thousands of machines with no off switch. That’s a strength for trust and a hazard for bugs, which is why testing matters so much.<\/p>\n\n\n\n
The term is older than Ethereum by two decades. Computer scientist and legal scholar Nick Szabo defined it in his 1996 paper Smart Contracts: Building Blocks for Digital Free Markets<\/em>:<\/p>\n\n\n\n “A smart contract is a set of promises, specified in digital form, including protocols within which the parties perform on these promises.” \u2014 Nick Szabo, 1996<\/a><\/p>\n<\/blockquote>\n\n\n\n On Ethereum, those “promises” are code, and the “protocol” is the Ethereum Virtual Machine (EVM)<\/a> \u2014 the runtime that executes contract code identically on every node in the network.<\/p>\n\n\n Because it separates the workflow from the logic. Ethereum’s ecosystem is deep and full of moving parts, so a beginner needs one thing that works end to end before adding complexity.<\/p>\n\n\n\n Print a greeting, deploy it, read it back. The mechanics you learn on this tiny example are the same ones behind a token, an NFT collection, or a lending market \u2014 only the logic in the middle grows.<\/p>\n\n\n Solidity is the main language for writing smart contracts on Ethereum and other EVM-compatible chains. It’s statically typed and looks a lot like JavaScript with stricter rules, which was a deliberate choice to make it approachable for web developers.<\/p>\n\n\n\n Solidity was proposed in 2014 and is maintained by a dedicated team under the Ethereum Foundation. It still moves quickly: the latest stable release is 0.8.37, published on September 10, 2026<\/a>. Your code compiles down to EVM bytecode, and the EVM works in 256-bit words \u2014 that’s why you’ll see types like Here’s why the language matters for a beginner. Solidity hides raw bytecode behind readable syntax, so you write logic instead of stack operations. That readability is also a safety feature, because a bug on a public chain is expensive and permanent, and code you can actually read is code you can actually audit.<\/p>\n\n\n Almost anyone building on Ethereum touches it eventually. The same first contract you’re about to write scales up to systems securing billions of dollars in on-chain value.<\/p>\n\n\n\n Common authors and their use cases include:<\/p>\n\n\n\n So “Hello World” isn’t a toy detour. It’s the on-ramp every one of these people started on.<\/p>\n\n\n You can write and deploy your first contract entirely in a browser, with nothing installed locally. The short list:<\/p>\n\n\n\n No node to install, no command line, no real money. That’s the whole point of starting here.<\/p>\n\n\n Open Remix, create a file called solidity<\/p>\n\n\n\n Each line has a job, and skipping any of them will trip the compiler or a warning.<\/p>\n\n\n\n That’s the smallest complete Solidity smart contract that does something visible. You didn’t write a single function, yet the contract already exposes readable data.<\/p>\n\n\n Reading a fixed string is a start, but the interesting part of any Solidity smart contract is changing state. Add one function so the greeting can be updated after deployment:<\/p>\n\n\n\n solidity<\/p>\n\n\n\n This introduces the single most important distinction in Ethereum development: reading versus writing.<\/p>\n\n\n\n The word Deployment is where the contract stops being text and becomes a live address on a blockchain. Work through these steps in order.<\/p>\n\n\n\n Once it’s live, expand the contract under Deployed Contracts<\/em> and click the blue One timing caveat worth knowing: Sepolia is late in its lifecycle, with an estimated end-of-life around September 30, 2026 and a successor testnet planned to run alongside it during a migration window. Always check a testnet’s current status before you commit a long project to it.<\/p>\n\n\n Remix is ideal for a first contract, but most teams eventually move to a local framework for testing and automation. The three dominant options in 2026 line up like this:<\/p>\n\n\n\n The practical rule: start in Remix, then adopt Hardhat if your team lives in JavaScript, or Foundry if you’d rather write tests in Solidity itself and care about speed.<\/p>\n\n\n\n When you deploy from Hardhat or Foundry to a public testnet or mainnet, the framework needs a connection to Ethereum to broadcast the transaction. Rather than running and syncing your own machine, many developers point the framework at a hosted Ethereum endpoint<\/a> and keep their attention on the contract. NOWNodes offers that access across 120+ networks, and its free public endpoints<\/a> are enough for early testing. For the command-line version of this workflow, see the walkthrough on deploying a smart contract on Ethereum<\/a>.<\/p>\n\n\n A first contract is forgiving. A production one is not, so it helps to learn the guardrails early.<\/p>\n\n\n\n\n
Why start with “Hello World”?<\/h3>\n\n\n
What Is Solidity, and Why Does Ethereum Use It?<\/h2>\n\n\n
uint256<\/code> all over Solidity code.<\/p>\n\n\n\nWho Uses Solidity in Practice?<\/h2>\n\n\n
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What You Need Before You Start<\/h2>\n\n\n
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Writing Your First Contract in Remix<\/h2>\n\n\n
HelloWorld.sol<\/code>, and paste in the contract below. One line of real state does all the work.<\/p>\n\n\n\n\/\/ SPDX-License-Identifier: MIT\npragma solidity ^0.8.0;\n\ncontract HelloWorld {\n string public greet = \"Hello, World!\";\n}<\/code><\/pre>\n\n\nBreaking down the code<\/h3>\n\n\n
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\/\/ SPDX-License-Identifier: MIT<\/code><\/strong> declares the software license. The compiler warns when it’s missing, so treat it as a required first line.<\/li>\n\n\n\npragma solidity ^0.8.0;<\/code><\/strong> sets which compiler versions are allowed. The caret ^<\/code> means “0.8.0 or any compatible 0.8.x release,” so it builds with 0.8.37 but rejects a breaking 0.9.0.<\/li>\n\n\n\ncontract HelloWorld { ... }<\/code><\/strong> declares the contract itself, much like a class in other languages.<\/li>\n\n\n\nstring public greet = \"Hello, World!\";<\/code><\/strong> creates a state variable stored permanently on-chain. The public<\/code> keyword tells Solidity to generate a free getter function automatically, so anyone can read greet<\/code> without you writing extra code.<\/li>\n<\/ol>\n\n\n\nMaking the Contract Interactive<\/h2>\n\n\n
\/\/ SPDX-License-Identifier: MIT\npragma solidity ^0.8.0;\n\ncontract HelloWorld {\n string public greet = \"Hello, World!\";\n\n function setGreeting(string memory _newGreeting) public {\n greet = _newGreeting;\n }\n}<\/code><\/pre>\n\n\n\n\n
greet<\/code> is free. It’s a view of existing data and needs no transaction.<\/li>\n\n\n\nsetGreeting<\/code> changes on-chain state, so it costs gas and requires a wallet-signed transaction that the whole network processes.<\/li>\n<\/ul>\n\n\n\nmemory<\/code> in the parameter tells Solidity where to hold _newGreeting<\/code> during the call \u2014 in temporary memory rather than permanent storage. Getting data location right is one of the first real skills a Solidity developer builds.<\/p>\n\n\nHow to Compile and Deploy to a Test Network<\/h2>\n\n\n
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11155111<\/code>), which Ethereum’s own documentation calls the recommended default testnet for application development. Skip Holesky \u2014 it was deprecated in September 2025 \u2014 and note that Hoodi exists for validator testing, not contract work.<\/li>\n\n\n\ngreet<\/code> button. It returns “Hello, World!” \u2014 read straight off the blockchain.<\/p>\n\n\n\nRemix vs. Hardhat vs. Foundry: Which Tool Should You Use?<\/h2>\n\n\n
Tool<\/th> Best for<\/th> Interface<\/th> Learning curve<\/th><\/tr><\/thead> Remix<\/strong><\/td> First contracts, quick experiments, teaching<\/td> Browser IDE<\/td> Lowest<\/td><\/tr> Hardhat<\/strong><\/td> JavaScript\/TypeScript teams, large plugin ecosystem<\/td> JS\/TS CLI<\/td> Moderate<\/td><\/tr> Foundry<\/strong><\/td> Fast testing and Solidity-native workflows<\/td> Solidity\/Rust CLI<\/td> Steeper<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n Common Mistakes and Limits to Know<\/h2>\n\n\n