apple-touch-iconfavicon.ico de facto standard which, while somewhat quirky in its use of the ico format, has been pretty much universally adopted elsewhere. Conversely, apple-touch-icon.png will be ignored by non-Apple devices, possibly because its 16x16 resolution would look pretty shabby on most smart phones. The icon can be provided in various different resolutions for different screen sizes and resolutions, e.g. apple-touch-icon-152x152.png for retina iPad with iOS7. (https://developer.apple.com/library/ios/documentation/AppleApplications/Reference/SafariWebContent/ConfiguringWebApplications/ConfiguringWebApplications.html) Apple documentation. https://realfavicongenerator.net/faq.
Last updated: 2018-08-19