XS

A programming language. Anywhere, anytime, by anyone.

One statically-linked binary contains the compiler, the language server, the debugger, the formatter, the linter, the test runner, the profiler, and the package manager. The same source runs unchanged on Linux, macOS, Windows, WASI, iOS, Android, ESP32, and Raspberry Pi.

fn fib(n) {
    if n < 2 { return n }
    return fib(n - 1) + fib(n - 2)
}

println(fib(30))    -- 832040

Both installers verify the GitHub release against its published SHA-256 sums before running anything. Static binaries with checksums also live at /downloads.

Benchmarks

startup, hello world

3 ms

fib(30) on the JIT

31 ms

fib(30) on the VM

180 ms

fib(30) on Node 20

62 ms

fib(30) on CPython 3.13

71 ms

binary size, stripped

2.9 MB

C source (excluding BearSSL)

132 KLOC

Measured on a Linux x86-64 box, each binary cold from disk, best of three runs. Reproduce with bash tests/bench_backends.sh in the source tree. The JIT and VM numbers come from the same build that ships in releases.

Backends

xs --interp

tree-walk interpreter

for the REPL and AST-level plugin debugging

xs (default)

bytecode VM

what normal runs go through

xs --jit

register-allocating JIT

x86-64 + aarch64; opcodes outside its set fall back to the VM

xs --emit c

C transpiler

self-contained C source for any reasonable compiler

xs --emit js

JavaScript transpiler

Node or the browser; ships less than xs.wasm if you only need one program

xs.wasm

runtime build

the same compiler running in a browser; ships a virtual filesystem and behaves like the native binary, so any XS program can be evaluated at runtime. how to embed it.