Byte-exact filesharing and 'picture sharing' are actually different usecases. Most people who casually exchange pictures are okay with some amount of lossy comp

Byte-exact filesharing and 'picture sharing' are actually different usecases. Most people who casually exchange pictures are okay with some amount of lossy compression if they can't visually tell the difference. Since you specifically mention that you're not okay with anything other than byte-exact sharing, this drastically limits your options and automatically excludes certain well-integrated solutions like Facebook. Your other constraints are: [1] Viewers must not be required to download an app they don't already have (ie. in your case Whatsapp and Email) [2] No size limit [3] Downloaded images appear in 'Camera roll', not a 'Downloads' folder Unfortunately, [3] is not possible on Android, as all browsers on Android save to a 'Downloads' folder, not the 'camera roll'; iOS on the other hand doesn't expose folders, so all saved images will appear in the 'camera roll' by default. [1] and [2] are readily offered by sharing on Google Drive, OneDrive, and other cloud providers. Make the file public 'shared by URL' and email/chat the URLs around.