Checkbox

Allow users to switch between checked, unchecked, and indeterminate states.

	<script lang="ts">
  import { Checkbox, Label } from "bits-ui";
  import Check from "phosphor-svelte/lib/Check";
  import Minus from "phosphor-svelte/lib/Minus";
</script>
 
<div class="flex items-center space-x-3">
  <Checkbox.Root
    id="terms"
    aria-labelledby="terms-label"
    class="peer inline-flex size-[25px] items-center justify-center rounded-md border border-muted bg-foreground transition-all duration-150 ease-in-out active:scale-98 data-[state=unchecked]:border-border-input data-[state=unchecked]:bg-background data-[state=unchecked]:hover:border-dark-40"
    name="hello"
  >
    {#snippet children({ checked })}
      <div class="inline-flex items-center justify-center text-background">
        {#if checked === true}
          <Check class="size-[15px]" weight="bold" />
        {:else if checked === "indeterminate"}
          <Minus class="size-[15px]" weight="bold" />
        {/if}
      </div>
    {/snippet}
  </Checkbox.Root>
  <Label.Root
    id="terms-label"
    for="terms"
    class="text-sm font-medium leading-none peer-disabled:cursor-not-allowed peer-disabled:opacity-70"
  >
    Accept terms and conditions
  </Label.Root>
</div>

Overview

The Checkbox component provides a flexible and accessible way to create checkbox inputs in your Svelte applications. It supports three states: checked, unchecked, and indeterminate, allowing for complex form interactions and data representations.

Key Features

  • Tri-State Support: Handles checked, unchecked, and indeterminate states, providing versatility in form design.
  • Accessibility: Built with WAI-ARIA guidelines in mind, ensuring keyboard navigation and screen reader support.
  • Flexible State Management: Supports both controlled and uncontrolled state, allowing for full control over the checkbox's checked state.

Architecture

The Checkbox component is composed of the following parts:

  • Root: The main component that manages the state and behavior of the checkbox.

Structure

Here's an overview of how the Checkbox component is structured in code:

	<script lang="ts">
	import { Checkbox } from "bits-ui";
</script>
 
<Checkbox.Root>
	{#snippet children({ checked })}
		{#if checked === "indeterminate"}
			-
		{:else if checked}
			✅
		{:else}
			❌
		{/if}
	{/snippet}
</Checkbox.Root>

Reusable Components

It's recommended to use the Checkbox primitive to create your own custom checkbox component that can be used throughout your application. In the example below, we're using the Checkbox and Label components to create a custom checkbox component.

MyCheckbox.svelte
	<script lang="ts">
	import { Checkbox, Label, useId, type WithoutChildrenOrChild } from "bits-ui";
 
	let {
		id = useId(),
		checked = $bindable(false),
		ref = $bindable(null),
		labelRef = $bindable(null),
		...restProps
	}: WithoutChildrenOrChild<Checkbox.RootProps> & {
		labelText: string;
		labelRef?: HTMLLabelElement | null;
	} = $props();
</script>
 
<Checkbox.Root bind:checked bind:ref {...restProps}>
	{#snippet children({ checked })}
		{#if checked === "indeterminate"}
			-
		{:else if checked}
			✅
		{:else}
			❌
		{/if}
	{/snippet}
</Checkbox.Root>
<Label.Root for={id} bind:ref={labelRef}>
	{labelText}
</Label.Root>

You can then use the MyCheckbox component in your application like so:

+page.svelte
	<script lang="ts">
	import MyCheckbox from "$lib/components/MyCheckbox.svelte";
</script>
 
<MyCheckbox labelText="Enable notifications" />

Managing Checked State

Bits UI offers several approaches to manage and synchronize the Checkbox's checked state, catering to different levels of control and integration needs.

1. Two-Way Binding

For seamless state synchronization, use Svelte's bind:checked directive. This method automatically keeps your local state in sync with the checkbox's internal state.

	<script lang="ts">
	import MyCheckbox from "$lib/components/MyCheckbox.svelte";
	let myChecked = $state(false);
</script>
 
<button onclick={() => (myChecked = false)}> uncheck </button>
 
<MyCheckbox bind:checked={myChecked} />

Key Benefits

  • Simplifies state management
  • Automatically updates myChecked when the checkbox changes (e.g., via clicking on the checkbox)
  • Allows external control (e.g., checking via a separate button/programmatically)

2. Change Handler

For more granular control or to perform additional logic on state changes, use the onCheckedChange prop. This approach is useful when you need to execute custom logic alongside state updates.

	<script lang="ts">
	import MyCheckbox from "$lib/components/MyCheckbox.svelte";
	let myChecked = $state(false);
</script>
 
<MyCheckbox
	checked={myChecked}
	onCheckedChange={(checked) => {
		myChecked = checked;
		if (checked === "indeterminate") {
			// do something different
		}
		// additional logic here.
	}}
/>

Use Cases

  • Implementing custom behaviors on checked/unchecked
  • Integrating with external state management solutions
  • Triggering side effects (e.g., logging, data fetching)

3. Fully Controlled

For complete control over the checkbox's checked state, use the controlledChecked prop. This approach requires you to manually manage the checked state, giving you full control over when and how the checkbox responds to change events.

To implement controlled state:

  1. Set the controlledChecked prop to true on the Checkbox.Root component.
  2. Provide a checked prop to Checkbox.Root, which should be a variable holding the current state.
  3. Implement an onCheckedChange handler to update the state when the internal state changes.
	<script lang="ts">
	import { Checkbox } from "bits-ui";
	let myChecked = $state(false);
</script>
 
<Checkbox.Root controlledChecked checked={myChecked} onCheckedChange={(c) => (myChecked = c)}>
	<!-- ... -->
</Checkbox.Root>

When to Use

  • Implementing complex checked/unchecked logic
  • Coordinating multiple UI elements
  • Debugging state-related issues

Disabled State

You can disable the checkbox by setting the disabled prop to true.

	<MyCheckbox disabled labelText="Enable notifications" />

HTML Forms

If you set the name prop, a hidden checkbox input will be rendered to submit the value of the checkbox with a form.

By default, the checkbox will be submitted with default checkbox value of 'on' if the checked prop is true.

	<MyCheckbox name="notifications" labelText="Enable notifications" />

Custom Input Value

If you'd prefer to submit a different value, you can use the value prop to set the value of the hidden input.

For example, if you wanted to submit a string value, you could do the following:

	<MyCheckbox value="hello" name="notifications" labelText="Enable notifications" />

Required

If you want to make the checkbox required, you can use the required prop.

	<Checkbox.Root required>
	<!-- ... -->
</Checkbox.Root>

This will apply the required attribute to the hidden input element, ensuring that proper form submission is enforced.

API Reference

Checkbox.Root

The button component used to toggle the state of the checkbox.

Property Type Description
checked $bindable
union

The checkbox button's checked state. This can be a boolean or the string 'indeterminate', which would typically display a dash in the checkbox.

Default: false
onCheckedChange
function

A callback that is fired when the checkbox button's checked state changes.

Default: undefined
controlledChecked
boolean

Whether or not the checked state is controlled or not. If true, the component will not update the checked state internally, instead it will call onCheckedChange when it would have otherwise, and it is up to you to update the checked prop that is passed to the component.

Default: false
disabled
boolean

Whether or not the checkbox button is disabled. This prevents the user from interacting with it.

Default: false
required
boolean

Whether or not the checkbox is required.

Default: false
name
string

The name of the checkbox. If provided a hidden input will be render to use for form submission. If not provided, the hidden input will not be rendered.

Default: undefined
value
string

The value of the checkbox. This is what is submitted with the form when the checkbox is checked.

Default: undefined
ref $bindable
HTMLButtonElement

The underlying DOM element being rendered. You can bind to this to get a reference to the element.

Default: undefined
children
Snippet

The children content to render.

Default: undefined
child
Snippet

Use render delegation to render your own element. See delegation docs for more information.

Default: undefined
Data Attribute Value Description
data-state
enum

The checkbox's state of checked, unchecked, or indeterminate.

data-disabled
''

Present when the checkbox is disabled.

data-checkbox-root
''

Present on the root element.