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Wes Bos

Wes Bos

Full Stack JavaScript Developer. Creator of really good web development courses. BBQ enthusiast.

Scott Tolinski

Scott Tolinski

Web Developer, Creator of Level Up Tuts, Bboy, Robotops Crew and Youtuber

Playing: 476: Browser CSS Page Transitions API aka Shared Element Transitions



Jun 27th, 2022

Browser CSS Page Transitions API aka Shared Element Transitions

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In this Hasty Treat, Scott and Wes talk about the new Browser CSS Page Transitions API proposal and what features it opens up for developers on the web.

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Show Notes

async function doTransition() {
  let transition = document.createDocumentTransition();

  // Specify offered elements. The tag below is used to refer
  // to the generated pseudo elemends in script/CSS.
  document.querySelector(".old-message").style.pageTransitionTag = "message";

  // The start() call triggers an async operation to capture
  // snapshots for the offered elements,
  await transition.start(async () => {
    // This callback is invoked by the browser when the capture
    // finishes and the DOM can be switched to the new state.
    // No frames are rendered until this callback returns.

    // Asynchronously load the new page.
    await coolFramework.changeTheDOMToPageB();

    // Clear the old message if that element is still in the page
    document.querySelector(".old-message").style.pageTransitionTag = "";
    // Set new message as the shared element 'message'
    document.querySelector(".new-message").style.pageTransitionTag = "message";

    // Set up animations using WA-API on the next frame.
    requestAnimationFrame(() => {
      document.documentElement.animate(keyframes, {
      pseudoElement: "::page-transition-container(message)",

    // Note that when this callback finishes, the animations will start with the tagged elements.

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