Flutter – Cross-platform mobile framework from Google
For some reason the website fails to prominently mention the two defining characteristics: it's based on Dart and it uses its own widget implementation.Honestly, between the use of a relatively exotic language of dubious quality with types that are "optional and unsound" (https://www.dartlang.org/articles/why-dart-types/), their custom widget implementation that who knows how well is going to work, and lack of web support, it doesn't seem very attractive.React-native seems a much safer bet.