Styling

• Tailwind CSS
  • Building your own Tailwind CSS theme
  • Additional styling overrides
• Installing the legacy Genesis CSS theme
• Outer attributes
• Custom classes
• Appending classes
• Resetting classes
• Removing classes
• Section-key class props
• Classes prop
• Classes configuration
  • Global class configuration
  • Class configuration on a group, list, or form
• Using generateClasses from @formkit/themes
• The rootClasses function
• Modifying classes within schema
  • Section-key class props within schema
  • Classes prop within schema
  • Config within schema

FormKit ships robust and accessible markup — but with no assumptions about your desired styles. FormKit provides optional themes you are welcome to use in your project — or you can create your own.

Tailwind CSS

Using the Web UI

The easiest way to get started with FormKit Tailwind Themes is to install the themes package and head to themes.formkit.com, customize a theme, and choose Download theme.

FormKit Themes

Versatile, configurable, MIT-licensed Tailwind themes for use in your projects. Spend less time styling — more time building.

Using the CLI

Alternatively, you can use the FormKit CLI to select a theme for your project. Run the following command in the same directory as your formkit.config.{ts|js} file:

npx formkit@latest theme

This command will create a formkit.theme.{ts|js} file in the root of your project. To complete the setup you will need to use the rootClasses from this theme file in your formkit.config.{ts|js}:

// formkit.config.ts
import { defaultConfig } from '@formkit/vue'
import { rootClasses } from './formkit.theme'

export default defaultConfig({
  config: {
    rootClasses,
  },
})

Finally, you’ll need to add the formkit.theme.{ts|js} file to your Tailwind config file’s content property. This will ensure that the theme’s styles are included in your project’s CSS:

// tailwind.config.js
/** @type {import('tailwindcss').Config} */
module.exports = {
  content: [
    "./app.vue",
    "./formkit.theme.ts" // <-- add your theme file
  ],
  darkMode: 'class',
  theme: {
    extend: {},
  },
  plugins: [],
}

If you run the command again, you will be taken to https://themes.formkit.com where you can customize your chosen theme.

# with existing formkit.theme file in your project root
> npx formkit@latest theme
? Found local theme file for <themeName>, edit this theme? › (Y/n)

Building your own Tailwind CSS theme

Want to create your own Tailwind theme? Check out our starter theme — which is heavily commented — to get started. You can also follow our guide, "Create a Tailwind CSS theme" to follow along step by step through the theme creation process.

Additional styling overrides

Continue reading to learn how to further override the classes that ship with your chosen FormKit theme at global, form, and input levels.

Installing the legacy Genesis CSS theme

CDN Usage

To load genesis via CDN, supply it to the theme property of your defaultConfig.

...
defaultConfig({
  theme: 'genesis' // will load from CDN and inject into document head
})
...

Direct import

To install Genesis, first install the @formkit/themes package.

npm install @formkit/themes

Then in your main.js (wherever you boot Vue up) include the Genesis theme.css (this assumes you are using a build tool like Vite, Webpack, Snowpack, or Nuxt):

import '@formkit/themes/genesis'

Outer attributes

For styling purposes some attributes are automatically added to and removed from the outer section of all FormKit inputs:

• data-type — The type of input, text, select, checkbox etc.
• data-multiple — For inputs that accept the multiple attribute, this will be appended when the input has the multiple attribute (like the select input).
• data-disabled — Present when an input is disabled.
• data-complete — Present when the input is "complete". Intended to be used for styling the input when a user has completed filling out the input (like a green checkmark). Read about context.state.complete for information what conditions cause this to be true.
• data-invalid — Present when the input has failing validation rules and the messages for the failing rules are visible.
• data-errors — Present when the input has explicitly set errors.

You can use the above attributes to easily provide realtime visual feedback for users filling out your forms:

Custom classes

Most users will want to apply their own styles and classes to FormKit's provided markup. FormKit provides numerous methods to apply classes for your project.

Classes can be modified for all sections using any of the following methods (from highest to lowest specificity):

• The {section-key}-class props. (most specific)
• The classes prop.
• The classes configuration option.
• The rootClasses configuration function. (least specific)

The classes follow a strict hierarchy. Initially, classes are produced by the rootClasses function. They can then be modified by the classes configuration option, then by the classes prop, and finally by the {section-key}-class prop. At each of these stages classes can be appended, reset, or selectively modified.

Appending classes

To append a class, simply return the string you want to append, or provide an object of classes with boolean values — true properties will be appended:

Resetting classes

Classes produced by all earlier hierarchy steps can be completely removed by providing a special (not rendered) class $reset in either string format or object format:

Removing classes

Classes produced by an earlier step in the class hierarchy can be selectively removed by providing an object with the value false for the class you want to remove or by providing a class name to a {section-key}-class prop that starts with $remove: and matches an existing class in the class list. This includes removing formkit's default formkit- prefixed classes:

Section-key class props

The simplest way to modify the classes of an element inside a FormKit input is via the {section-key}-class props. To add a class to a specific section element, like label, you simply add the label-class prop:

Classes prop

The classes prop is similar to the section-key class prop except it allows setting classes on all sections at the same time:

Classes configuration

The classes configuration option is similar to the classes prop, except it applies to all inputs the configuration is applied to. FormKit's unique configuration system allows for you to apply classes globally on your project or just inputs within a certain group or form:

Global class configuration

Class configuration on a group, list, or form

Using generateClasses from @formkit/themes

FormKit ships with a helper function called generateClasses included in @formkit/themes.

The generateClasses function takes a javascript object keyed by input type with values of a sub-object keyed by ${sectionKey} with values of strings. With this function you can quickly apply class lists to sections within inputs based on a given inputs' type.

The rootClasses function

rootClasses is a configuration function that is responsible for producing the default classes for each element. This function already has a default value which produces all the default classes (like formkit-outer and formkit-label) that ship with FormKit — so replacing this single function allows you to easily replace all initial classes. This makes it an ideal candidate for writing custom themes when using utility frameworks like Tailwind.

The rootClasses function is passed 2 arguments (respectively):

• The section key (like label or input).
• The input’s node.

The function will be called once for each section and it must return an object of classes with boolean values.

While typical usage of rootClasses is at the global config level to apply classes to your entire project - you can also use it with the config prop to override a specific form or input within your project with a class list computed from the logic within your provided function:

Modifying classes within schema

In addition to modifying classes via config or props on a <FormKit> component, you can use the same techniques within schema:

Section-key class props within schema

Within schema, you can also modify the classes of an element inside an input via the {section-key}Class properties. For example, to add a class to the label section, you can add the labelClass property:

{
  $formkit: 'text',
  name: 'email',
  // adds 'appended-class' to the "label" section
  labelClass: 'appended-class'
},

Classes prop within schema

Much like the classes prop on a <FormKit> component, you can modify the class list for any section of an input with the classes property on a schema node:

{
  $formkit: 'text',
  name: 'email',
  // modifies classes on both the "outer" and "inner" sections of this input
  classes: {
    outer: 'new-outer-class',
    inner: {
      $reset: true, // resets classes on the "inner" section
      'new-inner-class': true
    }
  },
},

Config within schema

Since config is passed down to descendant inputs, you can alter classes via config on a parent, such as a form, list, or a group, and this will affect all descendants to any depth: