I built a free online C compiler from scratch – here's how it works

I recently built CForge, a free online C and C++ compiler that runs
entirely in the browser. No signup. No ads. No installation.

Try it here: https://v0-online-c-complier.vercel.app

Why I built it

Most online C compilers either have too many ads, require an account,
or don't support basic things like stdin input or command line arguments.
I wanted something clean and fast.

How it works

The browser doesn't know how to compile C code. So here's what
actually happens when you click Run:

1. Your code is sent to a proxy API route
2. That route forwards it to Piston – an open source code execution engine running GCC 10.2
3. The output comes back in under a second and displays in the browser

That's it. No Docker on your machine. No backend you have to manage.

What it supports

• C and C++ (GCC 10.2)
• Standard input (scanf, cin)
• Command line arguments (argc, argv)
• Separate stdout, stderr and compile error display
• Shareable links – your code is encoded in the URL
• Auto-saves to localStorage so you don't lose work on refresh

Tech stack

• Next.js
• CodeMirror 6 (editor)
• Piston API (code execution)
• Vercel (hosting)

What's next

• Error line highlighting (click a compile error, jump to that line)
• More language support
• Dark/light theme toggle

Would love feedback from the community – especially C learners who
use online compilers regularly.