---
title: Theme
description: 'Learn how to customize Nuxt UI components using Tailwind CSS v4, CSS variables and the Tailwind Variants API for powerful and flexible theming.'
---

## Tailwind CSS

Nuxt UI v3 uses Tailwind CSS v4 alpha which doesn't have a documentation yet, let's have a look on how to use it.

### `@theme`

Tailwind CSS v4 takes a CSS-first configuration approach, you now customize your theme with CSS variables inside a `@theme` directive:

```css [main.css]
@import "tailwindcss";
@import "@nuxt/ui";

@theme {
  --font-sans: 'Public Sans', sans-serif;

  --breakpoint-3xl: 1920px;

  --color-green-50: #EFFDF5;
  --color-green-100: #D9FBE8;
  --color-green-200: #B3F5D1;
  --color-green-300: #75EDAE;
  --color-green-400: #00DC82;
  --color-green-500: #00C16A;
  --color-green-600: #00A155;
  --color-green-700: #007F45;
  --color-green-800: #016538;
  --color-green-900: #0A5331;
  --color-green-950: #052E16;
}
```

The `@theme` directive tells Tailwind to make new utilities and variants available based on these variables. It's the equivalent of the `theme.extend` key in Tailwind CSS v3 `tailwind.config.ts` file.

::note
You can learn more about this on [https://tailwindcss.com/blog/tailwindcss-v4-alpha](https://tailwindcss.com/blog/tailwindcss-v4-alpha#css-first-configuration).
::

### `@source`

You can use the `@source` directive to add explicit content glob patterns if you want to look for Tailwind classes in other files that are not automatically detected.

This can be useful when writing Tailwind classes in markdown files with [`@nuxt/content`](https://github.com/nuxt/content):

```css [main.css]
@import "tailwindcss";
@import "@nuxt/ui";

@source "../content/**/*.md";
```

::note{to="https://github.com/tailwindlabs/tailwindcss/pull/14078"}
You can learn more about the `@source` directive in this pull request.
::

### `@plugin`

You can use the `@plugin` directive to import Tailwind CSS plugins.

```css [main.css]
@import "tailwindcss";
@import "@nuxt/ui";

@plugin "@tailwindcss/typography";
```

::note{to="https://github.com/tailwindlabs/tailwindcss/pull/14264"}
You can learn more about the `@plugin` directive in this pull request.
::

## Design system

Nuxt UI extends Tailwind CSS's theming capabilities, providing a flexible design system with pre-configured color aliases and CSS variables. This allows for easy customization and quick adaptation of the UI to your brand's aesthetic.

### Colors

Nuxt UI leverages Nuxt [App Config](https://nuxt.com/docs/guide/directory-structure/app-config#app-config-file) to provide customizable color aliases based on [Tailwind CSS colors](https://tailwindcss.com/docs/customizing-colors#color-palette-reference):

| Color | Default | Description |
| --- | --- | --- |
| `primary`{color="primary"} | `green` | Main brand color, used as the default color for components. |
| `secondary`{color="secondary"} | `blue` | Secondary color to complement the primary color. |
| `success`{color="success"} | `green` | Used for success states. |
| `info`{color="info"} | `blue` | Used for informational states. |
| `warning`{color="warning"} | `yellow` | Used for warning states. |
| `error`{color="error"} | `red` | Used for form error validation states. |
| `neutral` | `slate` | Neutral color for backgrounds, text, etc. |

You can configure these color aliases at runtime in your `app.config.ts` file under the `ui.colors` key, allowing for dynamic theme customization without requiring an application rebuild:

```ts [app.config.ts]
export default defineAppConfig({
  ui: {
    colors: {
      primary: 'blue',
      neutral: 'zinc'
    }
  }
})
```

::note
Try the :prose-icon{name="i-lucide-swatch-book" class="text-[var(--ui-primary)]"} theme picker in the header above to change `primary` and `neutral` colors.
::

These colors are used to style the components but also to generate the `color` variants:

::component-code{slug="button"}
---
props:
  color: primary
slots:
  default: Button
---
::

::tip
You can add you own dynamic color aliases in your `app.config.ts`, you just have to make sure to define them in the [`ui.theme.colors`](/getting-started/installation#themecolors) option in your `nuxt.config.ts` file.

```ts [app.config.ts]
export default defineAppConfig({
  ui: {
    colors: {
      tertiary: 'indigo'
    }
  }
})
```

```ts [nuxt.config.ts]
export default defineNuxtConfig({
  ui: {
    theme: {
      colors: ['primary', 'secondary', 'tertiary', 'info', 'success', 'warning', 'error']
    }
  }
})
```

::

::warning
These color aliases are not automatically defined as Tailwind CSS colors, so classes like `text-primary-500 dark:text-primary-400` won't be available by default as in Nuxt UI v2. This approach provides more flexibility and prevents overwriting of user-defined Tailwind CSS colors.<br><br>

However, you can generate these classes using Tailwind's `@theme` directive, allowing you to use custom color utility classes while maintaining dynamic color aliases:

```css [main.css]
@import "tailwindcss";
@import "@nuxt/ui";

@theme {
  --color-primary-50: var(--ui-color-primary-50);
  --color-primary-100: var(--ui-color-primary-100);
  --color-primary-200: var(--ui-color-primary-200);
  --color-primary-300: var(--ui-color-primary-300);
  --color-primary-400: var(--ui-color-primary-400);
  --color-primary-500: var(--ui-color-primary-500);
  --color-primary-600: var(--ui-color-primary-600);
  --color-primary-700: var(--ui-color-primary-700);
  --color-primary-800: var(--ui-color-primary-800);
  --color-primary-900: var(--ui-color-primary-900);
  --color-primary-950: var(--ui-color-primary-950);
}
```
::

### Tokens

Nuxt UI leverages a robust system of CSS variables as design tokens to ensure consistent and flexible component styling. These tokens form the foundation of the theming system, offering smooth support for both light and dark modes.

#### Color Shades

Nuxt UI automatically creates a CSS variable for each color alias you define which represent the default shade used in both light and dark modes:

::code-group

```css [Light]
:root {
  --ui-primary: var(--ui-color-primary-500);
  --ui-secondary: var(--ui-color-secondary-500);
  --ui-success: var(--ui-color-success-500);
  --ui-info: var(--ui-color-info-500);
  --ui-warning: var(--ui-color-warning-500);
  --ui-error: var(--ui-color-error-500);
}
```

```css [Dark]
.dark {
  --ui-primary: var(--ui-color-primary-400);
  --ui-secondary: var(--ui-color-secondary-400);
  --ui-success: var(--ui-color-success-400);
  --ui-info: var(--ui-color-info-400);
  --ui-warning: var(--ui-color-warning-400);
  --ui-error: var(--ui-color-error-400);
}
```

::

::note
You can use these variables in classes like `text-[var(--ui-primary)]`, it will automatically adapt to the current color scheme.
::

::tip
You can change which shade is used for each color on light and dark mode:

```css [main.css]
@import "tailwindcss";
@import "@nuxt/ui";

:root {
  --ui-primary: var(--ui-color-primary-700);
}

.dark {
  --ui-primary: var(--ui-color-primary-200);
}
```
::

#### Neutral Palette

Nuxt UI provides a comprehensive set of design tokens for the `neutral` color palette, ensuring consistent and accessible UI styling across both light and dark modes. These tokens offer fine-grained control over text, background, and border colors:

::code-group

```css [Light]
:root {
  /* Least prominent text */
  --ui-text-dimmed: var(--ui-color-neutral-400);
  /* Slightly muted text */
  --ui-text-muted: var(--ui-color-neutral-500);
  /* Moderately prominent text */
  --ui-text-toned: var(--ui-color-neutral-600);
  /* Default text color */
  --ui-text: var(--ui-color-neutral-700);
  /* Most prominent text */
  --ui-text-highlighted: var(--ui-color-neutral-900);

  /* Main background color */
  --ui-bg: var(--color-white);
  /* Subtle background */
  --ui-bg-muted: var(--ui-color-neutral-50);
  /* Slightly elevated background */
  --ui-bg-elevated: var(--ui-color-neutral-100);
  /* More prominent background */
  --ui-bg-accented: var(--ui-color-neutral-200);
  /* Inverted background color */
  --ui-bg-inverted: var(--ui-color-neutral-900);

  /* Default border color */
  --ui-border: var(--ui-color-neutral-200);
  /* Subtle border */
  --ui-border-muted: var(--ui-color-neutral-200);
  /* More prominent border */
  --ui-border-accented: var(--ui-color-neutral-300);
  /* Inverted border color */
  --ui-border-inverted: var(--ui-color-neutral-900);
}
```

```css [Dark]
.dark {
  /* Least prominent text */
  --ui-text-dimmed: var(--ui-color-neutral-500);
  /* Slightly muted text */
  --ui-text-muted: var(--ui-color-neutral-400);
  /* Moderately prominent text */
  --ui-text-toned: var(--ui-color-neutral-300);
  /* Default text color */
  --ui-text: var(--ui-color-neutral-200);
  /* Most prominent text */
  --ui-text-highlighted: var(--color-white);

  /* Main background color */
  --ui-bg: var(--ui-color-neutral-900);
  /* Subtle background */
  --ui-bg-muted: var(--ui-color-neutral-800);
  /* Slightly elevated background */
  --ui-bg-elevated: var(--ui-color-neutral-800);
  /* More prominent background */
  --ui-bg-accented: var(--ui-color-neutral-700);
  /* Inverted background color */
  --ui-bg-inverted: var(--color-white);

  /* Default border color */
  --ui-border: var(--ui-color-neutral-800);
  /* Subtle border */
  --ui-border-muted: var(--ui-color-neutral-700);
  /* More prominent border */
  --ui-border-accented: var(--ui-color-neutral-700);
  /* Inverted border color */
  --ui-border-inverted: var(--color-white);
}
```

::

::note
Nuxt UI automatically applies a text and background color on the `<body>` element of your app:

```css
body {
  @apply antialiased text-[var(--ui-text)] bg-[var(--ui-bg)];
}
```
::

::tip
You can customize these CSS variables to tailor the appearance of your application:

```css [main.css]
@import "tailwindcss";
@import "@nuxt/ui";

:root {
  --ui-bg: var(--ui-color-neutral-50);
  --ui-text: var(--ui-color-neutral-900);
}

.dark {
  --ui-bg: var(--ui-color-neutral-950);
  --ui-border: var(--ui-color-neutral-900);
}
```
::

#### Border Radius

Nuxt UI uses a global `--ui-radius` CSS variable for consistent border rounding. Components use variations of this base value, like `rounded-[calc(var(--ui-radius)*2)]`, to create different levels of roundness throughout the UI:

```css
:root {
  --ui-radius: var(--radius-sm);
}
```

::note
Try the :prose-icon{name="i-lucide-swatch-book" class="text-[var(--ui-primary)]"} theme picker in the header above to change the base radius value.
::

::tip
You can customize the default radius value using the default Tailwind CSS variables or a value of your choice:

```css [main.css]
@import "tailwindcss";
@import "@nuxt/ui";

:root {
  --ui-radius: var(--radius-sm);
}
```
::

#### Container

Nuxt UI uses a global `--ui-container` CSS variable to define the width of the container:

```css
:root {
  --ui-container: var(--container-7xl);
}
```

::tip
You can customize the default container width using the default Tailwind CSS variables or a value of your choice:

```css [main.css]
@import "tailwindcss";
@import "@nuxt/ui";

@theme {
  --container-8xl: 90rem;
}

:root {
  --ui-container: var(--container-8xl);
}
```
::

## Components theme

Nuxt UI components are styled using the [Tailwind Variants](https://www.tailwind-variants.org/) API, which provides a powerful way to create variants and manage component styles. Let's explore the key features of this API:

### Slots

Components in Nuxt UI can have multiple `slots`, each representing a distinct HTML element or section within the component. These slots allow for flexible content insertion and styling. Let's take the [Card](/components/card) component as an example:

::code-group

```ts [src/theme/card.ts]
export default {
  slots: {
    root: 'bg-[var(--ui-bg)] ring ring-[var(--ui-border)] divide-y divide-[var(--ui-border)] rounded-[calc(var(--ui-radius)*2)] shadow-sm',
    header: 'p-4 sm:px-6',
    body: 'p-4 sm:p-6',
    footer: 'p-4 sm:px-6'
  }
}
```

```vue [src/runtime/components/Card.vue]
<template>
  <div :class="ui.root({ class: [props.class, props.ui?.root] })">
    <div :class="ui.header({ class: props.ui?.header })">
      <slot name="header" />
    </div>

    <div :class="ui.body({ class: props.ui?.body })">
      <slot />
    </div>

    <div :class="ui.footer({ class: props.ui?.footer })">
      <slot name="footer" />
    </div>
  </div>
</template>
```

::

Some components don't have slots, they are just composed of a single root element. In this case, the theme only defines the `base` slot like the [Container](/components/container) component for example:

::code-group

```ts [src/theme/container.ts]
export default {
  base: 'max-w-[var(--ui-container)] mx-auto px-4 sm:px-6 lg:px-8'
}
```

```vue [src/runtime/components/Container.vue]
<template>
  <div :class="container({ class: props.class })">
    <slot />
  </div>
</template>
```

::

::warning
Components without slots don't have a [`ui` prop](#ui-prop), only the [`class` prop](#class-prop) is available to override styles.
::

### Variants

Nuxt UI components use `variants` to change the `slots` styles based on props. Here's an example of the [Avatar](/components/avatar) component:

```ts [src/theme/avatar.ts]
export default {
  slots: {
    root: 'inline-flex items-center justify-center shrink-0 select-none overflow-hidden rounded-full align-middle bg-[var(--ui-bg-elevated)]',
    image: 'h-full w-full rounded-[inherit] object-cover'
  },
  variants: {
    size: {
      sm: {
        root: 'size-7 text-sm'
      },
      md: {
        root: 'size-8 text-base'
      },
      lg: {
        root: 'size-9 text-lg'
      }
    }
  },
  defaultVariants: {
    size: 'md'
  }
}
```

This way, the `size` prop will apply the corresponding styles to the `root` slot:

::component-code{slug="avatar"}
---
ignore:
  - src
props:
  src: 'https://github.com/nuxt.png'
  size: lg
---
::

The `defaultVariants` property specifies the default values for each variant. It determines how a component looks and behaves when no prop is provided. These default values can be customized in your [`app.config.ts`](#appconfigts) to adjust the standard appearance of components throughout your application.

## Customize theme

You have multiple ways to customize the appearance of Nuxt UI components, you can do it for all components at once or on a per-component basis.

::note
Tailwind Variants uses [tailwind-merge](https://github.com/dcastil/tailwind-merge) under the hood to merge classes so you don't have to worry about conflicting classes.
::

::tip
You can explore the theme for each component in two ways:

- Check the `Theme` section in the documentation of each individual component.
- Browse the source code directly in the GitHub repository at https://github.com/nuxt/ui/tree/v3/src/theme.
::

### `app.config.ts`

You can override the theme of components inside your `app.config.ts` by using the exact same structure as the theme object.

Let's say you want to change the font weight of all your buttons, you can do it like this:

```ts [app.config.ts]
export default defineAppConfig({
  ui: {
    button: {
      slots: {
        base: 'font-bold'
      }
    }
  }
})
```

::note
In this example, the `font-bold` class will override the default `font-medium` class on all buttons.
::

### `ui` prop

You can also override a component's **slots** using the `ui` prop. This has priority over the `app.config.ts` configuration and `variants` resolution.

::component-code{slug="button"}
---
prettier: true
ignore:
  - ui.trailingIcon
  - color
  - variant
  - size
  - icon
props:
  trailingIcon: i-lucide-chevron-right
  size: md
  color: neutral
  variant: outline
  ui:
    trailingIcon: 'rotate-90 size-3'
slots:
  default: |

    Button
---
::

::note
In this example, the `trailingIcon` slot is overwritten with `size-3` even though the `md` size variant would apply a `size-5` class to it.
::

### `class` prop

The `class` prop allows you to override the classes of the `root` or `base` slot. This has priority over the `app.config.ts` configuration and `variants` resolution.

::component-code{slug="button"}
---
props:
  class: 'font-bold rounded-full'
slots:
  default: Button
---
::

::note
In this example, the `font-bold` class will override the default `font-medium` class on this button.
::
