How to Configure Strict CSS View-Transition-Old and New Animation-Play-State in Google Chrome

Modern interactive web experiences often require developers to control the exact playback lifecycle of UI animations. With the View Transition API, browsers capture outgoing and incoming snapshots and animate them automatically. However, in scenarios such as onboarding product tours, interactive gesture-driven drag navigations, or user-controlled scrubber carousels, developers may need to pause an in-flight view transition, inspect or verify intermediate DOM state, and resume playback based on user input. CSS provides the standard animation-play-state property to pause and resume animations on demand.

Configuring strict animation-play-state: paused and running across ::view-transition-old and ::view-transition-new in Google Chrome enables fine-grained animation orchestration without dismantling active pseudo-element structures.

Chromium View Transition Playback State Mechanics

When Chromium triggers a transition, the pseudo-elements execute CSS animations attached via stylesheets or the default user-agent style sheet:

::view-transition
 └─ ::view-transition-group(article-hero)
     └─ ::view-transition-image-pair(article-hero)
         ├─ ::view-transition-old(article-hero)
         └─ ::view-transition-new(article-hero)

By toggling a CSS class or data attribute on the root document element, developers can instantly freeze the active keyframe playback at its exact current frame:

/* Global transition freeze state */
html[data-transition-paused="true"]::view-transition-group(*),
html[data-transition-paused="true"]::view-transition-old(*),
html[data-transition-paused="true"]::view-transition-new(*) {
    animation-play-state: paused !important;
}

/* Active running state */
html[data-transition-paused="false"]::view-transition-group(*),
html[data-transition-paused="false"]::view-transition-old(*),
html[data-transition-paused="false"]::view-transition-new(*) {
    animation-play-state: running;
}

Interactive Scrubbing via JavaScript

To synchronize transition playback with a range slider or pointer drag gesture, developers can pause the CSS animation and advance keyframes programmatically using the Web Animations API (WAAPI):

const transition = document.startViewTransition(() => {
    updateInterfaceDOM();
});

transition.ready.then(() => {
    // Access underlying WAAPI animation tracks
    const anim = document.getAnimations().find(a => 
        a.effect?.target?.matches?.('::view-transition-new(article-hero)')
    );

    if (anim) {
        // Pause and bind to range input scrubber
        anim.pause();
        const slider = document.getElementById('transition-scrubber');
        slider.addEventListener('input', (e) => {
            anim.currentTime = (e.target.value / 100) * anim.effect.getTiming().duration;
        });
    }
});

Inspecting Playback States in Chrome DevTools

To inspect and debug paused transition states in Google Chrome:

1. Press F12 to open Chrome DevTools.
2. Open the Animations panel via Ctrl+Shift+P > Show Animations.
3. Trigger your state transition. Chrome DevTools automatically intercepts the animation track.
4. Click the Pause (||) button in DevTools to freeze playback across all active pseudo-elements.
5. Inspect the ::view-transition-old and ::view-transition-new layers in the Elements panel to verify layer bounds, typography alignment, and computed styles at the frozen point.

Configuring strict animation-play-state controls provides complete programmatic mastery over view transition keyframes in Google Chrome.