Canvas rendering

Canvas rendering is a Browser Isolation capability that optimizes performance for web applications using the HTML5 Canvas API (a browser feature that allows web applications to draw graphics directly on the page). It sends vector draw commands to the client instead of rasterized bitmaps (pixel images), reducing bandwidth consumption and improving frame rates for productivity applications.

How it works

Browser Isolation uses Network Vector Rendering (NVR) to send lightweight drawing instructions to the user's browser, rather than streaming rendered pixels or video of the page. However, HTML5 Canvas content previously required server-side rasterization (converting draw commands into pixel images), sending large bitmaps for every frame.

Canvas rendering extends NVR to Canvas-based applications by:

1. Capturing draw commands made to the HTML5 Canvas element.
2. Converting and sending those commands to the client as NVR instructions.
3. Rendering the Canvas content on the client onto an offscreen texture (a hidden drawing surface used for intermediate rendering).
4. Compositing (layering) the texture into the final document output.

Supported applications

Canvas rendering improves performance for productivity applications that rely on the HTML5 Canvas API:

Application	Improvement
Microsoft Word	10x bandwidth reduction
Microsoft Excel	Smooth scrolling and data entry
Microsoft PowerPoint	Fluid animations
Google Sheets	Consistent 30fps rendering
Google Maps	Smooth panning and zooming
Web-based terminals and AI notebooks	Fast and responsive text input and display

Limitations

Canvas rendering supports 2D Canvas contexts only. The following are not supported:

• WebGL and WebGPU contexts
• 3D graphics applications
• Advanced Canvas features requiring GPU acceleration

Enable or disable canvas rendering

Canvas rendering is on by default for all Browser Isolation customers. No configuration is required.

Disable canvas rendering for the current session

1. Right-click on the background of the isolated webpage.
2. Select Disable Canvas Rendering from the context menu.

Re-enable canvas rendering

1. Right-click on the background of the isolated webpage.
2. Select Enable Canvas Rendering from the context menu.

Troubleshooting

Canvas content renders slowly

If Canvas-based applications appear choppy or consume excessive bandwidth:

1. Verify canvas rendering is on by right-clicking the page background.
2. Check that the context menu shows Disable Canvas Rendering (indicating it is active).
3. If the issue persists, open a support case and provide the Ray ID from the error page.

Graphical glitches or missing elements

If Canvas content displays incorrectly after reconnecting from a network interruption:

1. Refresh the isolated page.
2. If the issue persists, select Disable Canvas Rendering from the right-click menu.
3. Re-enable canvas rendering after the page reloads.