Multi‑User Whiteboard (Local) - Online Shared Drawing

A multi-user local whiteboard allows multiple browser tabs or windows on the same device (or same origin) to draw and collaborate in real time on a shared canvas. It uses the BroadcastChannel API to instantly synchronize all drawing operations across open instances without needing a server.

Local sharing uses the browser's built-in BroadcastChannel API. When you draw something, the operation is instantly broadcast to all other open tabs of the same tool. Each tab maintains an identical operation history, ensuring all canvases stay perfectly synchronized in real time.

Yes! This whiteboard works completely offline. All drawing data stays on your device. The local sharing feature works between tabs on the same device without any internet connection required.

The whiteboard includes a freehand pen, eraser, straight line, rectangle, circle, and text tool. You can customize stroke color, line thickness, and toggle shape fill. All tools support undo/redo and are synchronized across tabs.

Click the download button in the toolbar to export your current canvas as a high-resolution PNG image. The export preserves the full quality of your drawing with a white background.

There is no hard limit on the number of simultaneous users. The BroadcastChannel API efficiently handles many tabs, though practical limits depend on your device's performance. Typically, 5-15 concurrent tabs work smoothly.

Drawing data is stored in memory and via the operation history. When all tabs are closed, the canvas state is lost. To preserve your work, use the export function to save your drawing as a PNG file before closing.

Yes! The whiteboard is fully responsive and supports touch input on smartphones and tablets. You can draw with your finger or a stylus. The toolbar adapts to smaller screens for comfortable mobile use.

All modern browsers support this tool: Chrome 54+, Firefox 38+, Edge 79+, Safari 15.4+, and Opera 41+. The BroadcastChannel API is widely supported across all major browsers.

You can undo your last action by clicking the undo button (arrow rotating left) in the toolbar or pressing Ctrl+Z (Cmd+Z on Mac). Redo is available via Ctrl+Y (Cmd+Shift+Z on Mac) or the redo button. Undo/redo works across all connected tabs.