Creating Persistent App Tours

Web features: Popover Anchor positioning

Onboarding tours require overlays that persist while users interact with the highlighted features. Unlike auto popovers, manual popovers do not close when the user clicks elsewhere on the page. Combining popover="manual" with CSS Anchor Positioning allows you to create non-modal, tethered tour steps.

HTML

<div id="feature-target">Highlight this feature</div>

<!-- MANDATORY: Enforce overlay dialog semantics and accessible name bindings -->
<div id="tour-step" popover="manual" role="dialog" aria-labelledby="tour-title">
  <!-- Assume an <h1> precedes this element in the full document outline -->
  <h2 id="tour-title">Step 1</h2>
  <p>Learn how to use this feature.</p>
  <button popovertarget="tour-step" popovertargetaction="hide">Got it</button>
</div>

CSS

#feature-target {
  anchor-name: --feature-target;
}

#tour-step {
  popover: manual;
  position-anchor: --feature-target;
  position-area: right center;
  inset: auto;
  margin: 1rem;
  padding: 1rem;
  border: 1px solid blue;
  border-radius: 0.5rem;
  background: aliceblue;
}

JavaScript

const tourStep = document.getElementById('tour-step');
tourStep.showPopover();
// MANDATORY: Programmatically route focus into the non-modal popover so keyboard/assistive technology users immediately perceive the new context
tourStep.querySelector('button').focus();

Implementation Guidelines

  • MANDATORY: Use popover="manual" to prevent the tour step from closing accidentally during user interaction.
  • MANDATORY: Mark the container with role="dialog" and link its heading via aria-labelledby.
  • MANDATORY: Shift programmatic focus inside the popover immediately after opening to prevent focus abandonment.
  • DO use CSS Anchor Positioning to tether the tour step to the specific feature being explained.
  • DO provide an explicit "Close" or "Next" button within the popover that uses popovertargetaction="hide".

Fallback strategies

Fallbacks & browser support for Popover

The Popover API is mostly progressive enhancement, but its defining behaviors — top-layer promotion, light-dismiss, and popovertarget invocation — have no CSS-only equivalent. Older browsers need a polyfill, or a manual fallback if you would rather not ship one.

Polyfill: To support the popover attribute in older browsers, conditionally load @oddbird/popover-polyfill. MANDATORY: Feature detect by checking for the popover property on HTMLElement.prototype, and load the polyfill only when native support is missing — do NOT load it unconditionally.

With a bundler or import map:

// MANDATORY: Feature detect 'popover' on HTMLElement.prototype.
if (!("popover" in HTMLElement.prototype)) {
  import("@oddbird/popover-polyfill");
}

Without a bundler, import from a CDN inside a <script type="module">:

<script type="module">
  if (!("popover" in HTMLElement.prototype)) {
    import("https://unpkg.com/@oddbird/popover-polyfill@latest/dist/popover.min.js");
  }
</script>

Styling caveat: The polyfill cannot define the real :popover-open pseudo-class, so it applies a .\:popover-open class instead. MANDATORY: Combine the two with :is() or :where(), otherwise browsers that lack :popover-open discard the entire rule:

[popover]:is(:popover-open, .\:popover-open) {
  display: block;
}

Alternatively, for a legacy fallback without a polyfill, use position: fixed and manually calculate coordinates via getBoundingClientRect() or rely on default positioning with inset: auto if that's acceptable for the use case.

anchor-positioning

To support browsers without anchor positioning, you can choose between using a polyfill or a pure CSS fallback.

Option 1: Polyfill Fallback

The @oddbird/css-anchor-positioning polyfill can be used to emulate anchor positioning. It does not support implicit anchors, so you MUST add explicit anchor names to the trigger. Additionally, position-area is not supported on popovers by the polyfill, so you MUST use anchor() on the desired insets instead of position-area.

<script type="module">
  if (!CSS.supports('anchor-name: --foo')) {
    await import("https://unpkg.com/@oddbird/css-anchor-positioning");
  }
</script>

#tour-step {
  /* If using the anchor positioning polyfill with a popover, DO use `anchor()` functions instead of `position-area`. */
  left: anchor(right);
  top: anchor(top);
}
Option 2: Non-Polyfill CSS Fallback

If you prefer not to use a polyfill, you can default the tooltip to a fixed position at the bottom of the viewport using @supports not.

@supports not (anchor-name: --foo) {
  #tour-step {
    position: fixed;
    bottom: 0;
    left: 0;
    right: 0;
    width: 100%;
    margin: 0;
    border-radius: 0;
  }
}