How to run a GitHub project locally — 5 steps from clone to localhost

You found a ready-made project on GitHub — a template, a tutorial example, an app from an article — and want to run it yourself. Spoiler about the main trap: downloading the code is the easiest step, one command. What actually fails is a step you can't see in the repository: the .env file the author deliberately didn't publish.

Let's walk the whole path in order — five steps, about fifteen minutes.

1. Clone the repository

On the project page, hit the green "Code" button, copy the address, and run in the terminal:

git clone https://github.com/author/project.git
cd project

The first command downloads the repository into a folder next to you; the second steps inside.

There's also a "Download ZIP" button — it works, but clone is better: the full change history arrives with the code, and when the author updates the project, one git pull is enough instead of re-downloading.

2. Read the README

Two minutes that save an hour. Open README.md — it's rendered right on the project page — and find the "Getting Started" or "Installation" section.

That's where the author writes the exact launch commands for this specific project: which package manager, which Node version, which keys you'll need. If the README disagrees with this article — the README wins.

3. Install the dependencies

npm install

A project almost never lives in the repository in full: the node_modules folder with third-party libraries is left out on purpose — it weighs hundreds of megabytes and can be fully rebuilt from the list in package.json. This command asks the package manager to download everything on that list.

Don't panic when hundreds of packages scroll by in the terminal — that's normal: dependencies pull their own dependencies.

4. Create .env — the step where it breaks

Here's the trap from the intro. Most projects need secrets: API keys, a database address. They're never committed to the repository — that would be unsafe — so "half your project" is missing, and nothing warns you in red.

Look for a .env.example file in the root — it's a template with empty values. Copy it:

cp .env.example .env

— and fill it in. The variable names tell you what goes where: OPENAI_API_KEY — your key from the OpenAI dashboard, DATABASE_URL — your database address. Don't have the keys — you can almost always create them for free by searching the service name.

If the project starts but acts weird — check .env first: environment variables have their own pitfalls, from typos in names to invisible spaces.

5. Run it

The launch command lives in package.json under scripts. Most often it's:

npm run dev

The terminal prints an address like http://localhost:3000 — open it in the browser.

What you get

Your own copy of the project running on your computer. It's fully yours: change the code — the page updates live. This is also the best way to learn: open the project in your editor, ask AI to explain the structure, and make changes to a living app instead of a vacuum.

If it didn't start, the three most common causes, in order:

• A Node version error ("requires Node >= …") — update Node to the version from the README.
• Port 3000 is already in use — another of your projects is sitting on the port: how to free it.
• Crashes immediately complaining about an undefined variable — go back to step 4: most likely a missing key in .env.

Can I do this without the terminal?

Almost: GitHub Desktop clones with a button, and editors like VS Code and Cursor have "Clone Repository" right in the UI. But npm install and the launch still live in the terminal — learning three commands is easier than avoiding them.

Why run other people's projects at all?

It's the fastest start for your own: take a template, run it, repaint it — quicker than building from scratch. And it's the most honest way to learn: a living project with working code answers "how do people actually do this" better than any tutorial.