v143 · capabilities (fugu)

Web App Manifest: specify update eligibility, icon urls are Cache-Control: immutable

Specify an update eligibility algorithm in the manifest spec. This makes the update process more deterministic and predictable, giving the dev more control over whether (and when) updates should apply to existing installations, and allowing removal of the 'update check throttle' that user agents currently need to implement to avoid wasting network resources.

concepts

  1. Manifest Update Hints

    Edit old vs new manifest JSON and watch v143's eligibility algorithm decide: silent update, update dialog, or skip-icon-check — based on update_eligibility.icon_urls and Cache-Control: immutable.

  2. Icon immutability

    The Cache-Control: immutable half of the spec. Type URLs and headers, see whether v143 would re-fetch the icon — the biggest bytes-saved optimisation for PWAs that update manifests often.

  3. Update Policy Builder

    A manifest editor (name, start URL, update_via_cache, icons) with an icon cache policy toggle (immutable vs default) and staleness calculator. A version bump simulator analyses update-trigger eligibility per update_via_cache mode, and a live manifest JSON preview updates on every field change with a download export button.

why it shipped

- Consistency: Provide a consistent way to detect when a manifest update should happen. - Preventing unnecessary user interruption: Users should not see an update dialog more than necessary to confirm security-sensitive changes. - User agent flexibility: It should be possible for users agents to use their judgement to block updates for known bad sites, allow known trusted apps to update without UX, or allow tiny visual changes to icons without requiring UX. - Developer control: Developers should have more control over when the update dialog may show to users. - Reduce network traffic: Unnecess

references