MistCSS

Simplicity is the ultimate sophistication

MistCSS lets you create reusable visual components without JavaScript or TypeScript (think about it for a second... no JS/TS needed).

Leverage native HTML and CSS, get type safety and autocomplete. Just clean and efficient styling.

What you see above is standard HTML (data-attributes) and CSS (nested CSS). MistCSS simply creates a d.ts file based on your CSS.

• 🥶 Below zero-runtime, it's zero JavaScript. Smaller bundles and faster code.
• 💎 What you write is what you get. No transformations, easy debugging.
• 🎒 Standards-based, reusable styles across frameworks, compatible with Tailwind or any CSS framework
• ⚡️ Instantly productive, no learning curve, simple on-boarding.
• 💖 Back to basics with a modern twist: access the full power of HTML and CSS, enhanced with type safety and code completion (without the complexity).

This is general comparison and may vary depending on the library you're using.

Traditional approaches require wrapping your markup/styles in JavaScript functions (Button.tsx → <button/>, Input.tsx → <input/>, ...), defining props with TypeScript types, and writing logic to manage class names.

With MistCSS, styling is straightforward and minimal. Here’s how it looks:

mist.css

button {
  border-radius: 1rem;
  padding: 1rem;
  background: lightgray;

  &[data-variant='primary'] {
    background-color: black;
    color: white;
  }

  &[data-variant='secondary'] {
    background-color: grey;
    color: white;
  }
}

Page.tsx

<>
  <button data-variant="primary">Save</button>

  {/* TS error, tertiary isn't valid */}
  <button data-variant="tertiary">Save</button>
</>

Output

<button data-variant="primary">Save</button> {/* Same as in Page.tsx */}

This example demonstrates enums, but MistCSS also supports boolean and string props. For more details, see the FAQ.

MistCSS parses your mist.css file and generates mist.d.ts for type safety.

For instance, here’s the generated mist.d.ts for our button component:

interface Mist_button extends React.DetailedHTMLProps<React.HTMLAttributes<HTMLButtonElement>, HTMLButtonElement> {
  'data-variant'?: 'primary' | 'secondary'
}

declare namespace JSX {
  interface IntrinsicElements {
    button: Mist_button // ← <button/> is extended at JSX level to allow 'primary' and 'secondary' values
  }
}

That’s it! Simple yet powerful, built entirely on browser standards and TypeScript/JSX.

npm install mistcss --save-dev

postcss.config.js

module.exports = {
  plugins: {
    mistcss: {},
  },
}

layout.tsx

import './mist.css'

Absolutely, MistCSS is pure HTML and CSS, generating only mist.d.ts, so there are no limitations. You can integrate any CSS framework seamlessly. Here are a few examples to get you started:

button {
  @apply bg-blue-500 text-white;
  /* ... */
}

button {
  background: theme(colors.blue.500);
  /* ... */
}

Tailwind v4 will support CSS variables natively (see blog post).

To override some styles, you can use className

<button data-variant="primary" className="p-12">
  Save
</button>

button {
  background-color: var(--blue-6);
  /* ... */
}

CSS is more powerful than ever, before reaching for JS, explore if native CSS features can accomplish what you need.

No, using <name> would result in invalid HTML. However, this constraint is actually advantageous.

Firstly, it eliminates the risk of conflicts with native attributes:

<>
  <Button type="primary">Save</Button {/* Conflict with button's type="submit" */}
  <button data-type="primary">Save</button> {/* Safe */}
</>

Additionally, just by typing data- in your editor, autocomplete helps you clearly distinguish your custom attributes from standard tag attributes.

div[data-component='section']
  /* CSS variables */
  --color: ...;

  /* Default styles */
  background: var(--color, green);
  margin: ...;
  padding: ...;

  /* Enum props */
  &[data-size="sm"] { ... }
  &[data-size="lg"] { ... }

  /* Boolean props */
  &[data-is-active] { ... }

  /* Condition: size="lg" && is-active */
  &[data-size="lg"]&[data-is-active] { ... }

  /* Condition: size="lg" && !is-active */
  &[data-size="lg"]:not([data-is-active]) { ... }
}

<div
  data-component="section"
  data-size="foo"
  data-is-active
  style={{ '--color': 'red' }}
/>

If you want both basic links and button-styled links, here’s how you can do:

a:not([data-component]) { /* ... */ }

a[data-component='button'] {
  &[data-variant='primary'] { /* ... */ }
}

<>
  <a href="/home">Home</a>
  <a href="/home" data-component="button">Home</a>
  <a href="/home" data-component="button" data-variant="primary">Home</a>

  {/* TS error, `data-variant` is only valid with `data-component="button"` */}
  <a href="/home" data-variant="primary">Home</a>
</>

[!NOTE] > data-component is just a naming convention. Feel free to use any attribute, like data-kind='button' or just data-c. It’s simply a way to differentiate between components using the same tag.

You can use CSS @import. For example, in your mist.css file:

@import './button.css';

mist.css

article[data-component='card'] {
  /* ... */
}
div[data-component='card-title'] {
  /* ... */
}
div[data-component='card-content'] {
  /* ... */
}

Card.jsx

export function Card({ title, children }) {
  return (
    <article data-component="card">
      <div data-component="card-title">{title}</div>
      <div data-component="card-content">{children}</div>
    </article>
  )
}

:root {
  --primary-color: #007bff;
  --secondary-color: #6c757d;
}

button {
  background: var(--primary-color)
  /* ... */

See also your CSS framework/tooling documentation for ways to define them in JS if you prefer.

Assuming you have your UI components in a separate package my-ui and you're using Next.js, follow these steps:

app/layout.tsx

import 'my-ui/mist.css'

app/mist.d.ts

import 'my-ui/mist.d.ts

This setup ensures that your Next.js application correctly imports styles and type definitions from your external UI package. It may vary based on tools you're using, but the same principles should apply.

Mist is inspired by atomized water 💧 often seen near waterfalls. A nod to the Cascading in CSS 🌊.