Slider

A control element that allows for a range of selections.

Anatomy

To set up the slider correctly, you'll need to understand its anatomy and how we name its parts.

Each part includes a data-part attribute to help identify them in the DOM.

Examples

Learn how to use the Slider component in your project. Let's take a look at the most basic example:

import { Slider } from '@ark-ui/react/slider'

export const Basic = () => {
  return (
    <Slider.Root>
      <Slider.Label>Label</Slider.Label>
      <Slider.ValueText />
      <Slider.Control>
        <Slider.Track>
          <Slider.Range />
        </Slider.Track>
        <Slider.Thumb index={0}>
          <Slider.HiddenInput />
        </Slider.Thumb>
      </Slider.Control>
    </Slider.Root>
  )
}

import { Slider } from '@ark-ui/solid/slider'

export const Basic = () => {
  return (
    <Slider.Root>
      <Slider.Label>Label</Slider.Label>
      <Slider.ValueText />
      <Slider.Control>
        <Slider.Track>
          <Slider.Range />
        </Slider.Track>
        <Slider.Thumb index={0}>
          <Slider.HiddenInput />
        </Slider.Thumb>
      </Slider.Control>
    </Slider.Root>
  )
}

<script setup lang="ts">
import { Slider } from '@ark-ui/vue/slider'
</script>

<template>
  <Slider.Root>
    <Slider.Label>Label</Slider.Label>
    <Slider.ValueText />
    <Slider.Control>
      <Slider.Track>
        <Slider.Range />
      </Slider.Track>
      <Slider.Thumb :index="0" />
    </Slider.Control>
  </Slider.Root>
</template>

Range Slider

You can add multiple thumbs to the slider by adding multiple Slider.Thumb

import { Slider } from '@ark-ui/react/slider'

export const Range = () => {
  return (
    <Slider.Root defaultValue={[5, 10]}>
      <Slider.Label>Label</Slider.Label>
      <Slider.ValueText />
      <Slider.Control>
        <Slider.Track>
          <Slider.Range />
        </Slider.Track>
        <Slider.Thumb index={0}>
          <Slider.HiddenInput />
        </Slider.Thumb>
        <Slider.Thumb index={1}>
          <Slider.HiddenInput />
        </Slider.Thumb>
      </Slider.Control>
    </Slider.Root>
  )
}

import { Slider } from '@ark-ui/solid/slider'

export const Range = () => {
  return (
    <Slider.Root value={[5, 10]}>
      <Slider.Label>Label</Slider.Label>
      <Slider.ValueText />
      <Slider.Control>
        <Slider.Track>
          <Slider.Range />
        </Slider.Track>
        <Slider.Thumb index={0}>
          <Slider.HiddenInput />
        </Slider.Thumb>
        <Slider.Thumb index={1}>
          <Slider.HiddenInput />
        </Slider.Thumb>
      </Slider.Control>
    </Slider.Root>
  )
}

<script setup lang="ts">
import { Slider } from '@ark-ui/vue/slider'
</script>

<template>
  <Slider.Root :defaultValue="[10, 20]">
    <Slider.Label>Label</Slider.Label>
    <Slider.ValueText />
    <Slider.Control>
      <Slider.Track>
        <Slider.Range />
      </Slider.Track>
      <Slider.Thumb :index="0">
        <Slider.HiddenInput />
      </Slider.Thumb>
      <Slider.Thumb :index="1">
        <Slider.HiddenInput />
      </Slider.Thumb>
    </Slider.Control>
  </Slider.Root>
</template>

Adding marks

You can add marks to the slider track by using the Slider.MarkerGroup and Slider.Marker components.

Position the Slider.Marker components relative to the track by providing the value prop.

import { Slider } from '@ark-ui/react/slider'

export const WithMarks = () => {
  return (
    <Slider.Root>
      <Slider.Label>Label</Slider.Label>
      <Slider.ValueText />
      <Slider.Control>
        <Slider.Track>
          <Slider.Range />
        </Slider.Track>
        <Slider.Thumb index={0}>
          <Slider.HiddenInput />
        </Slider.Thumb>
      </Slider.Control>
      <Slider.MarkerGroup>
        <Slider.Marker value={0}>0</Slider.Marker>
        <Slider.Marker value={25}>*</Slider.Marker>
        <Slider.Marker value={50}>50</Slider.Marker>
        <Slider.Marker value={75}>*</Slider.Marker>
      </Slider.MarkerGroup>
    </Slider.Root>
  )
}

import { Slider } from '@ark-ui/solid/slider'

export const WithMarks = () => {
  return (
    <Slider.Root>
      <Slider.Label>Label</Slider.Label>
      <Slider.ValueText />
      <Slider.Control>
        <Slider.Track>
          <Slider.Range />
        </Slider.Track>
        <Slider.Thumb index={0}>
          <Slider.HiddenInput />
        </Slider.Thumb>
      </Slider.Control>
      <Slider.MarkerGroup>
        <Slider.Marker value={0}>0</Slider.Marker>
        <Slider.Marker value={25}>*</Slider.Marker>
        <Slider.Marker value={50}>50</Slider.Marker>
        <Slider.Marker value={75}>*</Slider.Marker>
      </Slider.MarkerGroup>
    </Slider.Root>
  )
}

<script setup lang="ts">
import { Slider } from '@ark-ui/vue/slider'
</script>

<template>
  <Slider.Root>
    <Slider.Label>Label</Slider.Label>
    <Slider.ValueText />
    <Slider.Control>
      <Slider.Track>
        <Slider.Range />
      </Slider.Track>
      <Slider.Thumb :key="0" :index="0" />
    </Slider.Control>
    <Slider.MarkerGroup>
      <Slider.Marker :value="0">0</Slider.Marker>
      <Slider.Marker :value="25">*</Slider.Marker>
      <Slider.Marker :value="50">50</Slider.Marker>
      <Slider.Marker :value="75">*</Slider.Marker>
    </Slider.MarkerGroup>
  </Slider.Root>
</template>

Setting the initial value

To set the slider's initial value, set the defaultValue prop to the array of numbers.

import { Slider } from '@ark-ui/react/slider'

export const InitialValue = () => (
  <Slider.Root defaultValue={[42]}>
    <Slider.Label>Label</Slider.Label>
    <Slider.ValueText />
    <Slider.Control>
      <Slider.Track>
        <Slider.Range />
      </Slider.Track>
      <Slider.Thumb index={0}>
        <Slider.HiddenInput />
      </Slider.Thumb>
    </Slider.Control>
    <Slider.MarkerGroup>
      <Slider.Marker value={0}>*</Slider.Marker>
      <Slider.Marker value={30}>*</Slider.Marker>
      <Slider.Marker value={60}>*</Slider.Marker>
    </Slider.MarkerGroup>
  </Slider.Root>
)

import { Slider } from '@ark-ui/solid/slider'

export const InitialValue = () => (
  <Slider.Root value={[42]}>
    <Slider.Label>Label</Slider.Label>
    <Slider.ValueText />
    <Slider.Control>
      <Slider.Track>
        <Slider.Range />
      </Slider.Track>
      <Slider.Thumb index={0}>
        <Slider.HiddenInput />
      </Slider.Thumb>
    </Slider.Control>
    <Slider.MarkerGroup>
      <Slider.Marker value={0}>*</Slider.Marker>
      <Slider.Marker value={30}>*</Slider.Marker>
      <Slider.Marker value={60}>*</Slider.Marker>
    </Slider.MarkerGroup>
  </Slider.Root>
)

<script setup lang="ts">
import { Slider } from '@ark-ui/vue/slider'
</script>

<template>
  <Slider.Root :model-value="[42]">
    <Slider.Label>Label</Slider.Label>
    <Slider.ValueText />
    <Slider.Control>
      <Slider.Track>
        <Slider.Range />
      </Slider.Track>
      <Slider.Thumb :key="0" :index="0" />
    </Slider.Control>
    <Slider.MarkerGroup>
      <Slider.Marker :value="0">*</Slider.Marker>
      <Slider.Marker :value="30">*</Slider.Marker>
      <Slider.Marker :value="60">*</Slider.Marker>
    </Slider.MarkerGroup>
  </Slider.Root>
</template>

Specifying the minimum and maximum

By default, the minimum is 0 and the maximum is 100. If that's not what you want, you can easily specify different bounds by changing the values of the min and/or max props.

For example, to ask the user for a value between -10 and 10, you can use:

import { Slider } from '@ark-ui/react/slider'

export const MinMax = () => {
  return (
    <Slider.Root min={-10} max={10}>
      <Slider.Label>Label</Slider.Label>
      <Slider.ValueText />
      <Slider.Control>
        <Slider.Track>
          <Slider.Range />
        </Slider.Track>
        <Slider.Thumb index={0}>
          <Slider.HiddenInput />
        </Slider.Thumb>
      </Slider.Control>
    </Slider.Root>
  )
}

import { Slider } from '@ark-ui/solid/slider'

export const MinMax = () => {
  return (
    <Slider.Root min={-10} max={10}>
      <Slider.Label>Label</Slider.Label>
      <Slider.ValueText />
      <Slider.Control>
        <Slider.Track>
          <Slider.Range />
        </Slider.Track>
        <Slider.Thumb index={0}>
          <Slider.HiddenInput />
        </Slider.Thumb>
      </Slider.Control>
    </Slider.Root>
  )
}

<script setup lang="ts">
import { Slider } from '@ark-ui/vue/slider'
</script>

<template>
  <Slider.Root :min="-10" :max="10">
    <Slider.Label>Label</Slider.Label>
    <Slider.ValueText />
    <Slider.Control>
      <Slider.Track>
        <Slider.Range />
      </Slider.Track>
      <Slider.Thumb :key="0" :index="0" />
    </Slider.Control>
  </Slider.Root>
</template>

Setting the value's granularity

By default, the granularity, is 1, meaning that the value is always an integer. You can change the step attribute to control the granularity.

For example, If you need a value between 5 and 10, accurate to two decimal places, you should set the value of step to 0.01:

import { Slider } from '@ark-ui/react/slider'

export const Step = () => {
  return (
    <Slider.Root step={0.01} min={5} max={10}>
      <Slider.Label>Label</Slider.Label>
      <Slider.ValueText />
      <Slider.Control>
        <Slider.Track>
          <Slider.Range />
        </Slider.Track>
        <Slider.Thumb index={0}>
          <Slider.HiddenInput />
        </Slider.Thumb>
      </Slider.Control>
    </Slider.Root>
  )
}

import { Slider } from '@ark-ui/solid/slider'

export const Step = () => {
  return (
    <Slider.Root step={0.01} min={5} max={10}>
      <Slider.Label>Label</Slider.Label>
      <Slider.ValueText />
      <Slider.Control>
        <Slider.Track>
          <Slider.Range />
        </Slider.Track>
        <Slider.Thumb index={0}>
          <Slider.HiddenInput />
        </Slider.Thumb>
      </Slider.Control>
    </Slider.Root>
  )
}

<script setup lang="ts">
import { Slider } from '@ark-ui/vue/slider'
</script>

<template>
  <Slider.Root :step="0.01" :min="5" :max="10">
    <Slider.Label>Label</Slider.Label>
    <Slider.ValueText />
    <Slider.Control>
      <Slider.Track>
        <Slider.Range />
      </Slider.Track>
      <Slider.Thumb :key="0" :index="0" />
    </Slider.Control>
  </Slider.Root>
</template>

Listening for changes

When the slider value changes, the onValueChange and onValueChangeEnd callbacks are invoked. You can use this to set up custom behaviors in your app.

import { Slider } from '@ark-ui/react/slider'

export const OnEvent = () => {
  return (
    <Slider.Root
      onValueChange={(details) => console.log(details.value)}
      onValueChangeEnd={(details) => console.log(details.value)}
    >
      <Slider.Label>Label</Slider.Label>
      <Slider.ValueText />
      <Slider.Control>
        <Slider.Track>
          <Slider.Range />
        </Slider.Track>
        <Slider.Thumb index={0}>
          <Slider.HiddenInput />
        </Slider.Thumb>
      </Slider.Control>
    </Slider.Root>
  )
}

import { Slider } from '@ark-ui/solid/slider'

export const OnEvent = () => {
  return (
    <Slider.Root
      onValueChange={(details) => console.log(details.value)}
      onValueChangeEnd={(details) => console.log(details.value)}
    >
      <Slider.Label>Label</Slider.Label>
      <Slider.ValueText />
      <Slider.Control>
        <Slider.Track>
          <Slider.Range />
        </Slider.Track>
        <Slider.Thumb index={0}>
          <Slider.HiddenInput />
        </Slider.Thumb>
      </Slider.Control>
    </Slider.Root>
  )
}

<script setup lang="ts">
import { Slider } from '@ark-ui/vue/slider'
</script>

<template>
  <Slider.Root
    @value-change="(details) => console.log(details.value)"
    @value-change-end="(details) => console.log(details.value)"
  >
    <Slider.Label>Label</Slider.Label>
    <Slider.ValueText />
    <Slider.Control>
      <Slider.Track>
        <Slider.Range />
      </Slider.Track>
      <Slider.Thumb :key="0" :index="0" />
    </Slider.Control>
  </Slider.Root>
</template>

Changing the orientation

By default, the slider is assumed to be horizontal. To change the orientation to vertical, set the orientation property in the machine's context to vertical.

In this mode, the slider will use the arrow up and down keys to increment/decrement its value.

Don't forget to change the styles of the vertical slider by specifying its height

import { Slider } from '@ark-ui/react/slider'

export const Vertical = () => {
  return (
    <Slider.Root orientation="vertical">
      <Slider.Label>Label</Slider.Label>
      <Slider.ValueText />
      <Slider.Control>
        <Slider.Track>
          <Slider.Range />
        </Slider.Track>
        <Slider.Thumb index={0}>
          <Slider.HiddenInput />
        </Slider.Thumb>
      </Slider.Control>
    </Slider.Root>
  )
}

import { Slider } from '@ark-ui/solid/slider'

export const Vertical = () => {
  return (
    <Slider.Root orientation="vertical">
      <Slider.Label>Label</Slider.Label>
      <Slider.ValueText />
      <Slider.Control>
        <Slider.Track>
          <Slider.Range />
        </Slider.Track>
        <Slider.Thumb index={0}>
          <Slider.HiddenInput />
        </Slider.Thumb>
      </Slider.Control>
    </Slider.Root>
  )
}

<script setup lang="ts">
import { Slider } from '@ark-ui/vue/slider'
</script>

<template>
  <Slider.Root orientation="vertical">
    <Slider.Label>Label</Slider.Label>
    <Slider.ValueText />
    <Slider.Control>
      <Slider.Track>
        <Slider.Range />
      </Slider.Track>
      <Slider.Thumb :key="0" :index="0" />
    </Slider.Control>
  </Slider.Root>
</template>

Changing the origin

By default, the slider's origin is at the start of the track. To change the origin to the center of the track, set the origin prop to center.

import { Slider } from '@ark-ui/react/slider'

export const CenterOrigin = () => {
  return (
    <Slider.Root origin="center">
      <Slider.Label>Label</Slider.Label>
      <Slider.ValueText />
      <Slider.Control>
        <Slider.Track>
          <Slider.Range />
        </Slider.Track>
        <Slider.Thumb index={0}>
          <Slider.HiddenInput />
        </Slider.Thumb>
      </Slider.Control>
    </Slider.Root>
  )
}

import { Slider } from '@ark-ui/solid/slider'

export const CenterOrigin = () => {
  return (
    <Slider.Root origin="center">
      <Slider.Label>Label</Slider.Label>
      <Slider.ValueText />
      <Slider.Control>
        <Slider.Track>
          <Slider.Range />
        </Slider.Track>
        <Slider.Thumb index={0}>
          <Slider.HiddenInput />
        </Slider.Thumb>
      </Slider.Control>
    </Slider.Root>
  )
}

<script setup lang="ts">
import { Slider } from '@ark-ui/vue/slider'
</script>

<template>
  <Slider.Root origin="center">
    <Slider.Label>Label</Slider.Label>
    <Slider.ValueText />
    <Slider.Control>
      <Slider.Track>
        <Slider.Range />
      </Slider.Track>
      <Slider.Thumb :key="0" :index="0" />
    </Slider.Control>
  </Slider.Root>
</template>

Using the Root Provider

The RootProvider component provides a context for the slider. It accepts the value of the useSlider hook. You can leverage it to access the component state and methods from outside the slider.

import { Slider, useSlider } from '@ark-ui/react/slider'

export const RootProvider = () => {
  const slider = useSlider()

  return (
    <>
      <button onClick={() => slider.focus()}>Focus</button>

      <Slider.RootProvider value={slider}>
        <Slider.Label>Label</Slider.Label>
        <Slider.ValueText />
        <Slider.Control>
          <Slider.Track>
            <Slider.Range />
          </Slider.Track>
          <Slider.Thumb index={0}>
            <Slider.HiddenInput />
          </Slider.Thumb>
        </Slider.Control>
      </Slider.RootProvider>
    </>
  )
}

import { Slider, useSlider } from '@ark-ui/solid/slider'

export const RootProvider = () => {
  const slider = useSlider()

  return (
    <>
      <button onClick={() => slider().focus()}>Focus</button>

      <Slider.RootProvider value={slider}>
        <Slider.Label>Label</Slider.Label>
        <Slider.ValueText />
        <Slider.Control>
          <Slider.Track>
            <Slider.Range />
          </Slider.Track>
          <Slider.Thumb index={0}>
            <Slider.HiddenInput />
          </Slider.Thumb>
        </Slider.Control>
      </Slider.RootProvider>
    </>
  )
}

<script setup lang="ts">
import { Slider, useSlider } from '@ark-ui/vue/slider'

const slider = useSlider()
</script>

<template>
  <button @click="slider.focus()">Focus</button>

  <Slider.RootProvider :value="slider">
    <Slider.Label>Label</Slider.Label>
    <Slider.ValueText />
    <Slider.Control>
      <Slider.Track>
        <Slider.Range />
      </Slider.Track>
      <Slider.Thumb :index="0" />
    </Slider.Control>
  </Slider.RootProvider>
</template>

If you're using the RootProvider component, you don't need to use the Root component.

API Reference

Root

Prop	Default	Type
`aria-label`		`string[]` The aria-label of each slider thumb. Useful for providing an accessible name to the slider
`aria-labelledby`		`string[]` The `id` of the elements that labels each slider thumb. Useful for providing an accessible name to the slider
`asChild`		`boolean` Use the provided child element as the default rendered element, combining their props and behavior. For more details, read our Composition guide.
`defaultValue`		`number[]` The initial value of the slider when it is first rendered. Use when you do not need to control the state of the slider picker.
`disabled`		`boolean` Whether the slider is disabled
`form`		`string` The associate form of the underlying input element.
`getAriaValueText`		`(details: ValueTextDetails) => string` Function that returns a human readable value for the slider thumb
`id`		`string` The unique identifier of the machine.
`ids`		`Partial<{ root: string thumb(index: number): string hiddenInput(index: number): string control: string track: string range: string label: string valueText: string marker(index: number): string }>` The ids of the elements in the range slider. Useful for composition.
`invalid`		`boolean` Whether the slider is invalid
`max`	`100`	`number` The maximum value of the slider
`min`	`0`	`number` The minimum value of the slider
`minStepsBetweenThumbs`	`0`	`number` The minimum permitted steps between multiple thumbs.
`name`		`string` The name associated with each slider thumb (when used in a form)
`onFocusChange`		`(details: FocusChangeDetails) => void` Function invoked when the slider's focused index changes
`onValueChange`		`(details: ValueChangeDetails) => void` Function invoked when the value of the slider changes
`onValueChangeEnd`		`(details: ValueChangeDetails) => void` Function invoked when the slider value change is done
`orientation`	`'horizontal'`	`'horizontal' \| 'vertical'` The orientation of the slider
`origin`	`'start'`	`'center' \| 'start'` The origin of the slider range - "start": Useful when the value represents an absolute value - "center": Useful when the value represents an offset (relative)
`readOnly`		`boolean` Whether the slider is read-only
`step`	`1`	`number` The step value of the slider
`thumbAlignment`	`'contain'`	`'center' \| 'contain'` The alignment of the slider thumb relative to the track - `center`: the thumb will extend beyond the bounds of the slider track. - `contain`: the thumb will be contained within the bounds of the track.
`thumbSize`		`{ width: number; height: number }` The slider thumbs dimensions
`value`		`number[]` The value of the range slider

Data Attribute	Value
`[data-scope]`	slider
`[data-part]`	root
`[data-disabled]`	Present when disabled
`[data-orientation]`	The orientation of the slider
`[data-dragging]`	Present when in the dragging state
`[data-invalid]`	Present when invalid
`[data-focus]`	Present when focused

Control

Prop	Default	Type
`asChild`		`boolean` Use the provided child element as the default rendered element, combining their props and behavior. For more details, read our Composition guide.

Data Attribute	Value
`[data-scope]`	slider
`[data-part]`	control
`[data-dragging]`	Present when in the dragging state
`[data-disabled]`	Present when disabled
`[data-orientation]`	The orientation of the control
`[data-invalid]`	Present when invalid
`[data-focus]`	Present when focused

HiddenInput

Prop	Default	Type
`asChild`		`boolean` Use the provided child element as the default rendered element, combining their props and behavior. For more details, read our Composition guide.

Label

Prop	Default	Type
`asChild`		`boolean` Use the provided child element as the default rendered element, combining their props and behavior. For more details, read our Composition guide.

Data Attribute	Value
`[data-scope]`	slider
`[data-part]`	label
`[data-disabled]`	Present when disabled
`[data-orientation]`	The orientation of the label
`[data-invalid]`	Present when invalid
`[data-dragging]`	Present when in the dragging state
`[data-focus]`	Present when focused

MarkerGroup

Prop	Default	Type
`asChild`		`boolean` Use the provided child element as the default rendered element, combining their props and behavior. For more details, read our Composition guide.

Data Attribute	Value
`[data-scope]`	slider
`[data-part]`	marker-group
`[data-orientation]`	The orientation of the markergroup

Marker

Prop	Default	Type
`value`		`number`
`asChild`		`boolean` Use the provided child element as the default rendered element, combining their props and behavior. For more details, read our Composition guide.

Data Attribute	Value
`[data-scope]`	slider
`[data-part]`	marker
`[data-orientation]`	The orientation of the marker
`[data-value]`
`[data-disabled]`	Present when disabled
`[data-state]`

Range

Prop	Default	Type
`asChild`		`boolean` Use the provided child element as the default rendered element, combining their props and behavior. For more details, read our Composition guide.

Data Attribute	Value
`[data-scope]`	slider
`[data-part]`	range
`[data-dragging]`	Present when in the dragging state
`[data-focus]`	Present when focused
`[data-invalid]`	Present when invalid
`[data-disabled]`	Present when disabled
`[data-orientation]`	The orientation of the range

RootProvider

Prop	Default	Type
`value`		`UseSliderReturn`
`asChild`		`boolean` Use the provided child element as the default rendered element, combining their props and behavior. For more details, read our Composition guide.

Thumb

Prop	Default	Type
`index`		`number`
`asChild`		`boolean` Use the provided child element as the default rendered element, combining their props and behavior. For more details, read our Composition guide.
`name`		`string`

Data Attribute	Value
`[data-scope]`	slider
`[data-part]`	thumb
`[data-index]`	The index of the item
`[data-name]`
`[data-disabled]`	Present when disabled
`[data-orientation]`	The orientation of the thumb
`[data-focus]`	Present when focused
`[data-dragging]`	Present when in the dragging state

Track

Prop	Default	Type
`asChild`		`boolean` Use the provided child element as the default rendered element, combining their props and behavior. For more details, read our Composition guide.

Data Attribute	Value
`[data-scope]`	slider
`[data-part]`	track
`[data-disabled]`	Present when disabled
`[data-invalid]`	Present when invalid
`[data-dragging]`	Present when in the dragging state
`[data-orientation]`	The orientation of the track
`[data-focus]`	Present when focused

ValueText

Prop	Default	Type
`asChild`		`boolean` Use the provided child element as the default rendered element, combining their props and behavior. For more details, read our Composition guide.

Data Attribute	Value
`[data-scope]`	slider
`[data-part]`	value-text
`[data-disabled]`	Present when disabled
`[data-orientation]`	The orientation of the valuetext
`[data-invalid]`	Present when invalid
`[data-focus]`	Present when focused

Accessibility

Complies with the Slider WAI-ARIA design pattern.

Keyboard Support

Key	Description
`ArrowRight`	Increments the slider based on defined step
`ArrowLeft`	Decrements the slider based on defined step
`ArrowUp`	Increases the value by the step amount.
`ArrowDown`	Decreases the value by the step amount.
`PageUp`	Increases the value by a larger step
`PageDown`	Decreases the value by a larger step
`Shift + ArrowUp`	Increases the value by a larger step
`Shift + ArrowDown`	Decreases the value by a larger step
`Home`	Sets the value to its minimum.
`End`	Sets the value to its maximum.