noVNC

noVNC implements the RFB (Remote Framebuffer / VNC) protocol entirely in JavaScript, using an HTML5 Canvas to render the remote screen and native browser input events to send keyboard/mouse/touch back to the server, with no browser plugin or native client required. Because the RFB protocol runs over a raw TCP socket that browsers can’t open directly, noVNC connects through websockify, a companion WebSocket-to-TCP proxy that both wrap the RFB stream for browser delivery.

The @novnc/novnc package exposes the core client as an importable RFB class (core/rfb.js) for embedding in custom applications, while the repository’s vnc.html/vnc_lite.html provide ready-made standalone pages. It is widely used as the browser-based console for virtualization and cloud platforms — including Proxmox VE, oVirt, OpenStack, and many other VNC-backed remote-access products.

What You Get

• An importable RFB client class (core/rfb.js) for embedding a VNC viewer in a custom web application
• Full RFB protocol implementation: multiple encodings, clipboard sync, and credential/auth negotiation
• Canvas-based rendering with support for touch, virtual keyboard, and mobile-friendly input handling
• Ready-to-use standalone pages (vnc.html, vnc_lite.html) for drop-in remote-desktop access
• Internationalized UI strings (po/ translations) for the bundled application shell

Common Use Cases

• Embedding a browser-based remote-desktop console in a virtualization or cloud management UI (VM consoles, hypervisor dashboards)
• Giving support/helpdesk tooling a no-plugin-required way to view and control a remote machine’s screen
• Providing kiosk or remote-lab access to a desktop environment purely through a web browser
• Building a custom remote-access product on top of the RFB client while supplying your own UI chrome

Under The Hood

Architecture - The core/ directory holds the protocol client: rfb.js drives the RFB handshake/state machine and owns a Display (display.js) for Canvas rendering and a Websock (websock.js) abstraction over the browser WebSocket API; decoders/ implements each supported RFB encoding (raw, hextile, tight, etc.) as a pluggable decoder, and input/ normalizes keyboard/mouse/touch events into RFB input messages.

Tech Stack - Modern vanilla JavaScript (ES modules, "type": "module" in package.json) with no framework dependency, a small vendor/ directory for pako (deflate) and legacy keysym tables, Karma + a fake-WebSocket test harness for browser-environment testing, and ESLint for style enforcement.

Code Quality - tests/ contains dedicated suites per module (test.display.js, test.deflator.js, test.copyrect.js, etc.) plus a fake.websocket.js harness that lets protocol logic be tested without a real VNC server, and a playback.js/playback-ui.js tool for replaying captured RFB sessions during debugging — a strong testing setup for a binary-protocol client.

API Design - Consumers instantiate new RFB(target, url, options) against a DOM element and a websockify-fronted WebSocket URL, then listen for connect/disconnect/credentialsrequired events; this is a comparatively low number of concepts for a full remote-desktop protocol client, though correctly standing up the required websockify proxy on the server side is an extra piece of infrastructure every integrator must provide.