Shadcn is a ready-to-use component library that you copy and paste directly into your project instead of installing it as a separate library.
In simple terms:
What's the idea?
Normally, when you use a design library (like Material UI or Bootstrap), you install a large package and are stuck with its style.
With Shadcn, it's the opposite:
You choose a button, a card, or a menu that's already designed and looks good.
You type a command, and the component's code appears directly IN your project.
The code belongs to you. You can change everything: colors, size, behavior.
It's not a library; it's a collection of recipes that you customize.
What's it made of?
Tailwind CSS for styling (classes like bg-black text-white)
Radix UI underneath for accessibility and robustness (keyboard, screen readers, etc.)
So you get the beauty of Tailwind + the robustness of Radix, without any hassle.
Why does everyone love it?
You remain in control: it's not a black box, it's your code.
Very beautiful by default: modern design, dark/light mode already handled.
Lightweight: you only take what you need. Just want a button? Just take the button.
In short: if you're building a website with Next.js/React and you want to move quickly without your site looking like everyone else's, shadcn gives you already beautiful building blocks that you can customize however you want.