If you're open to Forth,

https://github.com/remko/waforth

> WAForth is entirely written in (raw) WebAssembly, and the compiler generates WebAssembly code on the fly.

https://github.com/remko/waforth/blob/master/src/waforth.wat

> compiles to wasm in less than 1Mb of wasm

Janet, a Clojure-like Lisp compiles a whole playground of itself and the std lib in 823kb: https://janetdocs.org/playground

https://codeberg.org/veqq/janetdocs/src/branch/master/public...

you can do smaller for other things.

Ben Lynn's page https://crypto.stanford.edu/~blynn/compiler/ compiles (a large subset of) Haskell to web assembly (which you can download; a prime number sieve yielded 40KB of code) and runs it in the browser.

I'm working on a TypeScript/Swift/Dart style language, and currently this hello-world is 1444 bytes:

    export let main = () => {
      console.log("Hello, World!");
    };

I'm trying to make that smaller. The binary includes the Console class, which is needed (I may be able to tree-shake the non log() methods away), but also the Error and IndexOutOfBoundsError classes which aren't needed because there are no catch() expressions.

I think it really helps to have a language designed from the ground-up to obsess over bytes for WASM. Trying to do that with a familiar high-level language with a rich standard library is tricky.

C based Mandelbrot WASM demos can be ~1 KB total. Assuming you mean a simple scripting language though, Assembly Script does exactly that.

you can just compile c/c++ to wasm in the browser - there are wasi/emscripten builds of clang itself around (yosys, clang-repl, etc).

Also (on the bigger than this rather than smaller), Hoot, Spritely's Guile-on-Wasm project https://spritely.institute/hoot/