You're mixing a couple of ideas. There is a proposal[1] to allow for type annotations in the browser but it's only a subset of what's possible in TS. As for barreling/bundling, that's never been a goal for TypeScript. That's handled by tools like Webpack and ESBuild. In fact, there's an effort going the opposite direction. As browsers support ES style modules, we don't need to bundle anymore as the browser will load the relevant files as needed

[1] https://github.com/tc39/proposal-type-annotations

[2] https://developer.mozilla.org/en-US/docs/Web/JavaScript/Guid...