The programming language Google created for web development and Flutter is Dart.
Designed by Lars Bak and Kasper Lund and developed at Google, Dart was introduced in 2011 as a language for structured web programming. It uses a C-style syntax and supports object-oriented, class-based programming, garbage collection, interfaces, mixins, generics, and type inference. Dart code can be compiled in several ways, including to JavaScript, native machine code, and WebAssembly.
Dart became especially associated with Flutter, Google’s open-source, cross-platform UI framework. Flutter uses Dart to build applications for mobile, web, desktop, and other platforms from a shared codebase. Dart’s language features and Flutter’s widget-based design help developers create interfaces that look and behave consistently across devices.
TypeScript is another language commonly used for web development, but it was created by Microsoft and compiles to JavaScript. Kotlin is widely used for Android development, while Go is Google’s systems and backend language. Those distinctions make Dart the single canonical answer for this question.