[one-more-minute]

You need (a little) JS to run Wasm in the same way you need (a little) HTML to run JS; it's a hosted platform. JS handles loading and invoking the wasm code, and because it's close to a pure instruction set there's very little you can do without calling JS APIs, which in turn requires support code to translate across the boundary.

The WASI project specifies wasm-native APIs (modelled on posix) for running locally without JS, so you could imagine something similar for the browser. But the complexity of the DOM is forbidding.

I've not tried Emscripten hello world for a while, but I imagine it depends on things like optimisation level, dead code elim etc. In general to compile C code you'll need a malloc, string support and so on as you say. You can make the wasm file tiny if you lean on JS strings, but that increases the amount of support code again. Languages other than C will have an easier time reusing parts of the JS runtime (like strings or GC).

[josephg]

Yeah. And hello world is (thankfully) much smaller now than it used to be. Bigger than you think if you use printf, which is a quite complex C function. But at a guess, 10kb or something including support files. There are some great guides and tooling around to help shrink wasm size. Eg for rust:

https://rustwasm.github.io/docs/book/reference/code-size.htm...