platform_plus
Platform Plus is a package for easily figuring out information about the platform your code is running on.
Since dart:io is unavailable in web apps and dart:js is unavailable in native apps, the only way to do platform checks is with a conditional import like this:
import 'package:platform_plus/platform_mobile.dart'
if (dart.library.js) 'package:platform_plus/platform_web.dart';
That gets really annoying so this package handles it for you.
Getting Started
import 'package:platform_plus/platform_plus.dart';
platform.isAndroidNative;
platform.isAndroidWeb;
// And every other combination
await platform.isPhysicalDevice();