PR #531 routed the single-photo download through navigator.share()
whenever canShare({files}) returned true, on the assumption that any
mobile share sheet would expose a "Save Image" action. That holds on
iOS — Safari's share sheet has a first-party "Save to Photos" entry —
but on Android the system share sheet only lists installed apps that
registered an image/* intent (WhatsApp, Telegram, Drive, etc.). There
is no built-in save-to-Gallery action, so Android users tapping the
download button got an app-picker instead of the file saved to their
device.
Fix: gate the Web Share branch behind a UA-based isIOS() check. Android,
desktop, and everything else fall through to the existing <a download>
path (file lands in Downloads, visible in the Photos / Gallery app
afterwards — same behaviour as before #531). iOS — including iPadOS
13+, which reports as MacIntel + touch — keeps the share-sheet flow
that drops directly into Photos.
UA-sniff is the only available signal here: canShare({files}) is true
on both iOS Safari and Chrome Android, so feature detection cannot
distinguish them.
Tests pin all six scenarios — iOS share path, Android download fallback
(even with canShare=true), desktop, iPadOS-as-Mac detected as iOS, regular
Mac NOT detected as iOS, AbortError dismissal preserved (no surprise
fallback), and non-Abort share() rejection falls back to download.
Paul Nothaft
2a309c75a7