Lua doesn’t really run in browsers (except with emscripten or WASM? and also fengari (Lua interpreter written in JS with interop and GC sharing)) but for http luasocket / cqueues / openresty libs are good, and for servering also openresty seems good.

The equivalent for stb libs would be crossplatformness and in my experience they’ve worked for their advertised purpose on mac, windows, linux, android, ios.