Add EPUB file type support to Web Share API aka navigator.share()

[evangow]

The navigator.share() method doesn't currently support EPUB files, but readers want to be able to share EPUBs downloaded in the browser directly to their preferred reading app.

EPUB support in navigator.share() would be incredibly valuable to readers.

I've also submitted this request to Chromium, Webkit, and Firefox (links below).

https://issues.chromium.org/issues/40280918

https://bugs.webkit.org/show_bug.cgi?id=281152

https://connect.mozilla.org/t5/ideas/add-epub-file-type-support-to-web-share-api-aka-navigator-share/idi-p/73814

[marcoscaceres]

@evangow, I'm a bit confused about this request... why doesn't this work?:

const file = /* an ePub file gotten from somewhere */;
navigator.share({ files: [file] })

My understanding is that that should work (i.e., you can share any type of file with the API already).

[evangow]

According to MDN's docs, it's not included in the "shareable file types" https://developer.mozilla.org/en-US/docs/Web/API/Navigator/share#shareable_file_types

Thanks for the heads up though.

I guess those docs are wrong, because it does work in Safari at least, but Chrome throws a "NotAllowedError: Permission denied" error when trying to share an EPUB.

[jonathanKingston]

Chrome is currently restrictive based on mime and file types.

I personally think this should be relaxed to a deny list of obviously dubious filetypes.

Additionally the spec and current behaviour is somewhat non ideal in that this step applies to share and not canShare:

If document is not allowed to use "web-share", return a promise rejected with a "NotAllowedError" DOMException.

For example if the following throws on share:

const gpxFileContents = new File([blob], filename, { type: 'application/gpx+xml' });
const shareData = {
  files: [gpxFileContents]
}
if (navigator.canShare(shareData)) {
  await navigator.share(shareData);
}