Free Icons for All OS (Windows , Android , iOS , WEB).
Most of icons are available as regular images, both in *PNG *and *SVG *formats.
Icons for iOS
Icons also work well within iOS apps. In both the icons set, these icons are packaged up in Xcode imagesets which will work easily with Xcode Asset Catalogs (xcassets). These imagesets can be added to any Xcode Asset Catalogs by dragging them into Xcode on to the asset catalog or by copying the folder into the xcasset folder.