The checkbox input uses HTML's native checkbox input. It can display one or many options to a user and is a great way to allow users to select multiple items from a list. FormKit supports both single and multiple checkbox inputs.

Single checkbox

By default the checkbox type will render a single checkbox and uses boolean values. In order for a single checkbox to be checked — the current value of the input must match the on-value of that input (by default, a single checkbox uses true as the on-value).

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Checked Attribute Unnecessary

In order to improve API consistency across all FormKit inputs — FormKit uses the value as the initial state of the input. The checked prop/attribute should not be used directly.

Multiple checkboxes

To output multiple checkboxes with a single input use the options prop. Options can be specified 3 ways:

  • An array of strings
  • An object of value/label pairs
  • An array of objects with label and value properties (the same as the select and radio inputs)

The value of a checkbox input with multiple options is an array of the selected values.

Array of strings

The simplest way to provide options is an array of strings. The provided strings will be used for both the label and the value of the option.

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Value / Label object

You may also provide the options prop where the keys are values and the values of each property are labels.

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Array of objects

The most flexible way to define options is by providing an array of objects. The objects must include value and label properties — but may also include a help property as well as an attrs object of additional attributes to apply to each checkbox input tag.

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Props & Attributes

decorator-iconString’’Specifies an icon to put in the decoratorIcon section. Shows when the checkbox is checked. Defaults to the checkboxDecorator icon.
optionsArray/Object[]An object of value/label pairs or an array of strings, or an array of objects that must contain a label and value property.
on-valueanytrueThe value when the checkbox is checked (single checkboxes only).
off-valueanyfalseThe value when the checkbox is unchecked (single checkboxes only).
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configObject{}Configuration options to provide to the input’s node and any descendent node of this input.
delayNumber20Number of milliseconds to debounce an input’s value before the commit hook is dispatched.
dirtyBehaviorstringtouchedDetermines how the "dirty" flag of this input is set. Can be set to touched or comparetouched (the default) is more performant, but will not detect when the form is once again matching its initial state.
errorsArray[]Array of strings to show as error messages on this field.
helpString''Text for help text associated with the input.
idStringinput_{n}The unique id of the input. Providing an id also allows the input’s node to be globally accessed.
ignoreBooleanfalsePrevents an input from being included in any parent (group, list, form etc). Useful when using inputs for UI instead of actual values.
indexNumberundefinedAllows an input to be inserted at the given index if the parent is a list. If the input’s value is undefined, it inherits the value from that index position. If it has a value it inserts it into the lists’s values at the given index.
labelString''Text for the label element associated with the input.
nameStringinput_{n}The name of the input as identified in the data object. This should be unique within a group of fields.
parentFormKitNodecontextualBy default the parent is a wrapping group, list or form — but this props allows explicit assignment of the parent node.
prefix-iconString''Specifies an icon to put in the prefixIcon section.
preservebooleanfalsePreserves the value of the input on a parent group, list, or form when the input unmounts.
preserve-errorsbooleanfalseBy default errors set on inputs using setErrors are automatically cleared on input, setting this prop to true maintains the error until it is explicitly cleared.
sections-schemaObject{}An object of section keys and schema partial values, where each schema partial is applied to the respective section.
suffix-iconString''Specifies an icon to put in the suffixIcon section.
typeStringtextThe type of input to render from the library.
validationString, Array[]The validation rules to be applied to the input.
validation-visibilityStringblurDetermines when to show an input's failing validation rules. Valid values are blur, dirty, and live.
validation-labelString{label prop}Determines what label to use in validation error messages, by default it uses the label prop if available, otherwise it uses the name prop.
validation-rulesObject{}Additional custom validation rules to make available to the validation prop.
valueAnyundefinedSeeds the initial value of an input and/or its children. Not reactive. Can seed entire groups (forms) and lists..


The checkbox input has a different construction depending on if it's a single or multiple checkbox.

You can target a specific section of an input using that section's "key", allowing you to modify that section's classes, HTML (via :sections-schema, or content (via slots)). Read more about sections here.

Single checkbox diagram

I would like a free t-shirt
We will send a free-shirt if you have this box selected.
You must make a selection.

Multiple checkbox diagram

Choose the topics you`d like to learn this year.
We`ll be studying soil, plants, and seasons.
You must make a selection.
decoratorResponsible for the element immediately following the input element — usually used for styling custom checkboxes.
decoratorIconAn element containing the decorator icon.
legendResponsible for the fieldset’s legend element.
fieldsetResponsible for the fieldset when multiple options are available.
optionResponsible for the wrapper around each item in the options.
optionsResponsible for the wrapper element around all of the option items.
Show Universal section keys
outerThe outermost wrapping element.
wrapperA wrapper around the label and input.
labelThe label of the input.
prefixHas no output by default, but allows content directly before an input element.
prefixIconAn element for outputting an icon before the prefix section.
innerA wrapper around the actual input element.
suffixHas no output by default, but allows content directly after an input element.
suffixIconAn element for outputting an icon after the suffix section.
inputThe input element itself.
helpThe element containing help text.
messagesA wrapper around all the messages.
messageThe element (or many elements) containing a message — most often validation and error messages.