ui/docs/content/1.getting-started/3.theme.md

description

description
Learn how to customize the appearance of Nuxt UI components using Tailwind CSS.

Tailwind CSS

Since 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.

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

@import "tailwindcss";
@import "@nuxt/ui";

@theme {
  --font-family-display: "Inter", "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 those 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. ::

This is exactly what the @import "@nuxt/ui"; is all about, it extends the default Tailwind CSS theme and declares the primary, error and gray colors to be configurable through the App Config but we'll talk more about that in the Colors section.

Tailwind Variants API

Nuxt UI components are styled using the Tailwind Variants 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 component as an example:

::code-group

export default {
  slots: {
    root: 'bg-white dark:bg-gray-900 ring ring-gray-200 dark:ring-gray-800 divide-y divide-gray-200 dark:divide-gray-800 rounded-lg shadow',
    header: 'p-4 sm:px-6',
    body: 'p-4 sm:p-6',
    footer: 'p-4 sm:px-6'
  }
}

<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 component for example:

::code-group

export default {
  base: 'max-w-7xl mx-auto px-4 sm:px-6 lg:px-8'
}

<template>
  <div :class="container({ class: props.class })">
    <slot />
  </div>
</template>

::

::caution Components without slots don't have a ui prop, only the 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 component:

export default {
  slots: {
    root: 'inline-flex items-center justify-center shrink-0 select-none overflow-hidden rounded-full align-middle bg-gray-100 dark:bg-gray-800',
    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

ignore:

• src props: src: 'https://github.com/benjamincanac.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 to adjust the standard appearance of components throughout your application.

Customize components

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.

::tip Tailwind Variants uses tailwind-merge under the hood to merge classes so you don't have to worry about conflicting classes. ::

::note 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:

export default defineAppConfig({
  ui: {
    button: {
      slots: {
        base: 'font-bold'
      }
    }
  }
})

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

prettier: true ignore:

• ui.leadingIcon

• color

• variant

• size

• icon props: icon: i-heroicons-magnifying-glass size: md color: gray variant: outline ui: leadingIcon: 'text-primary-500 dark:text-primary-400 size-3' slots: default: |

  Button

---

::

In this example, the leadingIcon slot is overwritten even though the md size variant would apply a size-5 class by default.

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

props: class: 'font-bold rounded-full' slots: default: Button

::