The dream of being able to create universal apps is not new, but today, the challenge of creating an app that can run on several form factors is even more urgent. Just think of the many devices people use every day: smartphones, tablets, smartwatches, notebooks, smart TVs, gaming consoles, and desktop PCs. These are all clients where we, as developers, could potentially install our software.
Flutter has been supporting iOS and Android since the beginning, which already solves a huge need for developers, but it's taking huge steps in the direction of the dream of every developer: having a truly universal platform to develop apps that can run anywhere.
The Flutter implementation for the web was presented at Flutter Interact 2019 and is called Flutter for Web.
At the time I'm writing this, Flutter supports web development in the beta channel...