Safari-stack APNG: subtle timing differences vs Chrome, plus WKWebView networking and ATS on top
`safari-friendly-apng` targets iOS, macOS Safari, and WKWebView where APNG support is strong yet still gated by `Content-Type`, cross-origin caching, Low Power Mode, and Reduce Motion. Enterprise apps add custom caches or certificate pinning that accidentally serve only the first chunk. Test on hardware, and treat in-app WebView separately from standalone Safari.
Safari variant: validate `image/apng` and TLS, compare WebView vs browser, cover power-saver and reduced motion
- `curl -I` the CDN for correct MIME and no forced download headers; ensure security proxies are not truncating animated bodies.
- Open the same URL in WKWebView and Safari, record both; if only WebView fails, inspect custom `NSURLProtocol` hooks or offline packs that cached partial data.
- Re-test with Reduce Motion and Low Power Mode, documenting acceptable static fallbacks for accessibility rather than debating them post-launch.
Safari FAQ: WebView, MIME, power saver, reduced motion
macOS Safari plays, iOS WKWebView shows frame zero—network stack or decode?
Remote-debug the WebView: confirm full byte length and MIME. If bytes are complete yet static, look for interceptors replacing responses before blaming “no APNG.” Collect OS version evidence.
Reduce Motion freezes the APNG—marketing calls it a bug; do we override?
Ship intentional still alternates and treat it as compliance, not a defect. Measure how many users enable the setting before deciding on bespoke campaigns, but never bypass accessibility with JS hacks.
Safari and Chrome differ by tens of milliseconds on a beat-synced meme—how strict should QA be?
Metronome-record both, define acceptable jitter, and quantize delays to a 1/100 s grid at export if rounding causes drift. Pick a reference browser in the spec—pixel-perfect timing across engines is unrealistic.
MDM blocks third-party S3 hosts—APNG never loads; what architecture fixes it?
Serve from same-site origins or edge workers that proxy allowed hosts; update CSP `img-src`. Security should supply signed URLs and host allowlists instead of endless manual link edits.
TestFlight vs App Store builds cache differently—users see stale APNG; how to align?
Fingerprint URLs with versions or queries and document reinstall steps for QA. Confirm TestFlight and production hit the same bucket; mismatched cache keys mimic decoder bugs.