Run C 23 online

What's in C 23

• `nullptr` as a first-class null-pointer constant (finally).
• `typeof` operator standardised — no more GCC-only extension.
• The `#embed` preprocessor directive to embed binary blobs in source.

What you get in C 23

Clicking "Run now" opens the playground with this exact code and a matching test case — passes on first Run.

#include<stdio.h>
int main(){int n;scanf("%d",&n);printf("%d\n",n*2);return 0;}

How ls-judge runs C 23

Every submission is compiled and executed inside its own Firecracker microVM — the same isolation primitive AWS Lambda uses. No shared container, no shared kernel with other users' code. The C 23toolchain shipped with the microVM is the real thing (not a browser-side emulation): syscalls behave the way they do in production, and the compile / runtime behaviour matches what you would see on your own machine with that version installed.

Feed stdin from the Tests panel, watch verdicts stream per test case over a WebSocket. Free to use, no sign-up, works from any browser.