Live Compiler Pro: Building a Real-Time Code Editor with WebRTC

Live Compiler Pro is a browser-based IDE at live-code-hxft.onrender.com that supports multi-language editing, live preview, a built-in console, and real-time collaboration, ideal for pair programming, demos, and teaching.

The Idea

During college, I often wanted to code with friends remotely. Existing tools were either too heavy or required installations. I wanted something lightweight that works right in the browser, open the app, share a room code, and start coding together.

Core Features

• Multi-language editor, HTML, CSS, JavaScript, Python, JSON, and Markdown with syntax highlighting.
• Live preview, Run code manually or switch to Auto Run for instant HTML/CSS/JS updates.
• Built-in console, View logs, warnings, and errors; run JavaScript from the console input.
• Files & export, Create files, import from disk, rename tabs, and export as ZIP or individual files.
• Theme toggle, Dark and light modes for comfortable long sessions.
• Code snippets, Quick templates to bootstrap common patterns.

Live Collaboration (Collab)

The Collab button in the header opens the Live Collaboration panel, the heart of real-time pair programming in Live Compiler Pro. You can code together with classmates or teammates without installing anything extra.

Two ways to collaborate

• Anywhere (P2P), Connect with others over the internet using peer-to-peer networking. Best when you and your partner are on different networks or cities. The host sees a status badge (Connected / Host) and a shareable room code.
• Same Browser, Mirror code across tabs in the same browser with Tab Sync. Handy for testing responsive layouts or comparing two versions side by side without a network room.

How a live room works

1. Click Collab in the toolbar, then choose a username (shown to others in the room).
2. Create & Join Room, you become the host and receive a 12-character room code (for example HGAH1QTS29ST).
3. Share the code via Copy invite & share, teammates paste it under Join a room and click Join.
4. Everyone edits the same workspace in real time while the Chat sidebar stays open for live discussion.
5. Hosts can Reconnect if the session drops or Leave Room to end their participation.

Live Chat inside Collab rooms

Collaboration is not just shared code, you also get a built-in Chat panel on the left so you never have to switch to WhatsApp or Discord mid-debug. On Live Compiler Pro, chat is tied directly to the active room: text and images stay in the same thread as your live coding session.

Architecture

Backend

The server is built with Node.js and Express. Socket.io handles the WebSocket connections for real-time events:

const io = require('socket.io')(server);

io.on('connection', (socket) => {
    socket.on('code-change', (data) => {
        // Broadcast to all other users in the same room
        socket.to(data.room).emit('code-update', data.code);
    });

    socket.on('chat-message', (msg) => {
        io.to(msg.room).emit('new-message', msg);
    });
});

Frontend

The editor uses a code editor component with syntax highlighting. Changes are captured on every input event and emitted through Socket.io. Incoming updates are applied without disrupting the local user's cursor position.

Challenges

• Conflict resolution, When two users edit the same line simultaneously, changes can clash. I implemented a simple last-write-wins strategy which works well for small teams.
• Cursor management, Applying remote changes without jumping the local cursor was tricky. I track cursor offsets before and after applying updates.
• Room management, Each collaboration session gets a unique room ID. Users join by appending it to the URL.

What I Learned

This project deepened my understanding of WebSockets, real-time event architectures, and the challenges of collaborative editing. It also taught me how to structure a Node.js application for scalability.