View Transitions API Reference

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Added in: astro@3.0.0

These modules provide functions to control and interact with the View Transitions API and client-side router.

For features and usage examples, see our View Transitions guide.

Imports from astro:transitions

Section titled Imports from astro:transitions

import { ViewTransitions, fade, slide } from 'astro:transitions';

<ViewTransitions />

Section titled &lt;ViewTransitions /&gt;

Added in: astro@3.0.0

Opt in to using view transitions on individual pages by importing and adding the <ViewTransitions /> routing component to <head> on every desired page.

src/pages/index.astro

---import { ViewTransitions } from 'astro:transitions';---<html lang="en">  <head>    <title>My Homepage</title>    <ViewTransitions />  </head>  <body>    <h1>Welcome to my website!</h1>  </body></html>

See more about how to control the router and add transition directives to page elements and components.

fade

Section titled fade Type: (opts: { duration?: string | number }) => TransitionDirectionalAnimations

Added in: astro@3.0.0

Utility function to support customizing the duration of the built-in fade animation.

---import { fade } from 'astro:transitions';---
<!-- Fade transition with the default duration --><div transition:animate="fade" />
<!-- Fade transition with a duration of 400 milliseconds --><div transition:animate={fade({ duration: '0.4s' })} />

slide

Section titled slide Type: (opts: { duration?: string | number }) => TransitionDirectionalAnimations

Added in: astro@3.0.0

Utility function to support customizing the duration of the built-in slide animation.

---import { slide } from 'astro:transitions';---
<!-- Slide transition with the default duration --><div transition:animate="slide" />
<!-- Slide transition with a duration of 400 milliseconds --><div transition:animate={slide({ duration: '0.4s' })} />

Imports from astro:transitions/client

Section titled Imports from astro:transitions/client

<script>  import {    navigate,    supportsViewTransitions,    transitionEnabledOnThisPage,    getFallback,    swapFunctions,  } from 'astro:transitions/client';</script>

Section titled navigate() Type: (href: string, options?: Options) => void

Added in: astro@3.2.0

A function that executes a navigation to the given href using the View Transitions API.

This function signature is based on the navigate function from the browser Navigation API. Although based on the Navigation API, this function is implemented on top of the History API to allow for navigation without reloading the page.

history option

Section titled history option Type: 'auto' | 'push' | 'replace'

Default: 'auto'

Added in: astro@3.2.0

Defines how this navigation should be added to the browser history.

  • 'push': the router will use history.pushState to create a new entry in the browser history.
  • 'replace': the router will use history.replaceState to update the URL without adding a new entry into navigation.
  • 'auto' (default): the router will attempt history.pushState, but if the URL cannot be transitioned to, the current URL will remain with no changes to the browser history.

This option follows the history option from the browser Navigation API but simplified for the cases that can happen on an Astro project.

formData option

Section titled formData option Type: FormData

Added in: astro@3.5.0

A FormData object for POST requests.

When this option is provided, the requests to the navigation target page will be sent as a POST request with the form data object as the content.

Submitting an HTML form with view transitions enabled will use this method instead of the default navigation with page reload. Calling this method allows triggering the same behavior programmatically.

info option

Section titled info option Type: any

Added in: astro@3.6.0

Arbitrary data to be included in the astro:before-preparation and astro:before-swap events caused by this navigation.

This option mimics the info option from the browser Navigation API.

state option

Section titled state option Type: any

Added in: astro@3.6.0

Arbitrary data to be associated with the NavitationHistoryEntry object created by this navigation. This data can then be retrieved using the history.getState function from the History API.

This option mimics the state option from the browser Navigation API.

sourceElement option

Section titled sourceElement option Type: Element

Added in: astro@3.6.0

The element that triggered this navigation, if any. This element will be available in the following events:

  • astro:before-preparation
  • astro:before-swap

supportsViewTransitions

Section titled supportsViewTransitions Type: boolean

Added in: astro@3.2.0

Whether or not view transitions are supported and enabled in the current browser.

transitionEnabledOnThisPage

Section titled transitionEnabledOnThisPage Type: boolean

Added in: astro@3.2.0

Whether or not the current page has view transitions enabled for client-side navigation. This can be used to make components that behave differently when they are used on pages with view transitions.

getFallback()

Section titled getFallback() Type: () => 'none' | 'animate' | 'swap'

Added in: astro@3.6.0

Returns the fallback strategy to use in browsers that do not support view transitions.

See the guide on Fallback control for how to choose and configure the fallback behavior.

swapFunctions

Section titled swapFunctions

Added in: astro@4.15.0

An object containing the utility functions used to build Astro’s default swap function. These can be useful when building a custom swap function.

swapFunctions provides the following methods:

deselectScripts()

Section titled deselectScripts() Type: (newDocument: Document) => void

Marks scripts in the new document that should not be executed. Those scripts are already in the current document and are not flagged for re-execution using data-astro-rerun.

swapRootAttributes()

Section titled swapRootAttributes() Type: (newDocument: Document) => void

Swaps the attributes between the document roots, like the lang attribute. This also includes Astro-injected internal attributes like data-astro-transition, which makes the transition direction available to Astro-generated CSS rules.

When making a custom swap function, it is important to call this function so as not to break the view transition’s animations.

swapHeadElements()

Section titled swapHeadElements() Type: (newDocument: Document) => void

Removes every element from the current document’s <head> that is not persisted to the new document. Then appends all new elements from the new document’s <head> to the current document’s <head>.

saveFocus()

Section titled saveFocus() Type: () => () => void

Stores the element in focus on the current page and returns a function that when called, if the focused element was persisted, returns the focus to it.

swapBodyElement()

Section titled swapBodyElement() Type: (newBody: Element, oldBody: Element) => void

Replaces the old body with the new body. Then, goes through every element in the old body that should be persisted and have a matching element in the new body and swaps the old element back in place.

Lifecycle events

Section titled Lifecycle events

astro:before-preparation event

Section titled astro:before-preparation event An event dispatched at the beginning of a navigation using View Transitions. This event happens before any request is made and any browser state is changed.

This event has the attributes:

Read more about how to use this event on the View Transitions guide.

astro:after-preparation event

Section titled astro:after-preparation event An event dispatched after the next page in a navigation using View Transitions is loaded.

This event has no attributes.

Read more about how to use this event on the View Transitions guide.

astro:before-swap event

Section titled astro:before-swap event An event dispatched after the next page is parsed, prepared, and linked into a document in preparation for the transition but before any content is swapped between the documents.

This event can’t be canceled. Calling preventDefault() is a no-op.

This event has the attributes:

Read more about how to use this event on the View Transitions guide.

astro:after-swap event

Section titled astro:after-swap event An event dispatched after the contents of the page have been swapped but before the view transition ends.

The history entry and scroll position have already been updated when this event is triggered.

astro:page-load event

Section titled astro:page-load event An event dispatched after a page completes loading, whether from a navigation using view transitions or native to the browser.

When view transitions is enabled on the page, code that would normally execute on DOMContentLoaded should be changed to execute on this event.

Lifecycle events attributes

Section titled Lifecycle events attributes

Added in: astro@3.6.0

info

Section titled info Type: URL

Arbitrary data defined during navigation.

This is the literal value passed on the info option of the navigate() function.

sourceElement

Section titled sourceElement Type: Element | undefined

The element that triggered the navigation. This can be, for example, an <a> element that was clicked.

When using the navigate() function, this will be the element specified in the call.

newDocument

Section titled newDocument Type: Document

The document for the next page in the navigation. The contents of this document will be swapped in place of the contents of the current document.

Section titled navigationType Type: 'push' | 'replace' | 'traverse'

Which kind of history navigation is happening.

  • push: a new NavigationHistoryEntry is being created for the new page.
  • replace: the current NavigationHistoryEntry is being replaced with an entry for the new page.
  • traverse: no NavigationHistoryEntry is created. The position in the history is changing. The direction of the traversal is given on the direction attribute

direction

Section titled direction Type: Direction

The direction of the transition.

  • forward: navigating to the next page in the history or to a new page.
  • back: navigating to the previous page in the history.
  • Anything else some other listener might have set.

from

Section titled from Type: URL

The URL of the page initiating the navigation.

to

Section titled to Type: URL

The URL of the page being navigated to. This property can be modified, the value at the end of the lifecycle will be used in the NavigationHistoryEntry for the next page.

formData

Section titled formData Type: FormData | undefined

A FormData object for POST requests.

When this attribute is set, a POST request will be sent to the to URL with the given form data object as the content instead of the normal GET request.

When submitting an HTML form with view transitions enabled, this field is automatically set to the data in the form. When using the navigate() function, this value is the same as given in the options.

loader()

Section titled loader() Type: () => Promise<void>

Implementation of the following phase in the navigation (loading the next page). This implementation can be overridden to add extra behavior.

viewTransition

Section titled viewTransition Type: ViewTransition

The view transition object used in this navigation. On browsers that do not support the View Transitions API, this is an object implementing the same API for convenience but without the DOM integration.

swap()

Section titled swap() Type: () => void

Implementation of the document swap logic.

Read more about building a custom swap function in the View Transitions guide.

By default, this implementation will call the following functions in order:

  1. deselectScripts()
  2. swapRootAttributes()
  3. swapHeadElements()
  4. saveFocus()
  5. swapBodyElement()

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