Set up Master CSS in Astro

Guide to setting up Master CSS in your Astro project.

Master CSS Runtime Rendering observes changes in DOM class names at browser runtime, generates corresponding CSS rules, and injects them into the running style sheet.

Fixed style cost

All features work out of the box with ~16KB transfer cost

Fully automatic

Capture any program-generated class names

CSS lifecycle

CSS is generated on demand and frees memory when not in use

Quick start

Clone the example

Copy-paste the following commands to quickly start using the

You can skip all installation steps.

npx degit master-co/css/examples/astro-with-runtime-rendering my-project
cd my-project
npm install @master/css@beta
npm install
npm run dev


Create a project

If you don't have a Astro project, create one first. It's recommended to refer to Getting Started - Astro.

npm create astro@latest project
cd project

Install Master CSS

Install Master CSS into your project via package managers.

npm install @master/css@beta

Initialize configuration file

Run npx mcss init to create a configuration file master.css.ts.

npx mcss init

Set up CSS runtime engine

Modify src/layouts/Layout.astro:

  • Import your custom configuration master.css.ts
  • Initialize the runtime engine
  • Add display: none to <html> to avoid FOUC
<html style="display: none">
import { initRuntime } from "@master/css";
import config from "../../master.css";

Launch server

Run npm run dev to start your Astro development server

npm run dev

Start using Master CSS

Now style your first element using Master CSS syntax!

import Layout from '../layouts/Layout.astro';
<Layout title="Welcome to Astro.">
<h1 class="font:40 font:heavy italic m:50 text:center">Hello World</h1>

Open your browser to watch the changes.


Hello World

MIT License © Aoyue Design LLC.