Following my keynote at ng-conf 2017 that seemed to indicate that Typescript is now an official language at Google, there were many questions about the status of Dart at Google.
Dart has been used for unrestricted client development at Google now for 4+ years. Dart and AngularDart are used by large products such as AdWords, AdSense and Shopping, and by critical internal tools such as Google CRM. In addition, the Flutter cross-platform mobile app framework uses Dart and is used by multiple teams at Google including Google CRM and Shopping Express. The Google codebase contains many millions of lines of Dart code.
Typescript has become allowed for unrestricted client development as of March 2017. TypeScript and Angular on TypeScript are used in Google Analytics, Firebase, and Google Cloud Platform and critical internal tools such as bug tracking, employee reviews, and product approval and launch tools.We are happy to say that teams at Google have a choice between many client side languages and can choose the best one for their needs.