Review common troubleshooting scenarios for Cloudflare Browser Isolation.
If you encounter a No Browsers Available alert, please file feedback via the Cloudflare One Client. This error typically indicates a temporary capacity issue in the data center or a connectivity problem between your client and the remote browser.
This alert appears if your device attempts to establish more than two concurrent remote browser instances. A browser isolation session is shared across all tabs and windows within the same browser (for example, all Chrome tabs share one session). You can use two different browsers (such as Chrome and Firefox) concurrently, but opening a third will trigger this alert. To release a session, close all tabs and windows in one of your local browsers.
Browser Isolation supports one active window at a time. When you switch to a different isolated tab or window, Browser Isolation deactivates the previous window, pausing any audio or video playing there. This is expected behavior. For more details, refer to Single active window.
Cloudflare Browser Isolation uses Network Vector Rendering (NVR), which does not support WebGL (Web Graphics Library) in all environments. If a website requires WebGL and your device lacks the necessary hardware resources in the virtualized environment, you may see a rendering error.
To resolve this, try enabling software rasterization in your browser:
- Go to
chrome://flags/#override-software-rendering-list. - Set Override software rendering list to Enabled.
- Select Relaunch.
On Windows devices, Clientless Web Isolation may load with a blank screen if there is a conflict between browser mDNS settings and Windows IGMP configuration.
| IGMPLevel | WebRTC Anonymization | Result |
|---|---|---|
| 0 (disabled) | Enabled / Default | ❌ Blank screen |
| 0 (disabled) | Disabled | ✅ Works |
| 2 (enabled) | Enabled / Default | ✅ Works |
To fix this, either disable Anonymize local IPs exposed by WebRTC in your browser flags or ensure IGMPLevel is enabled (set to 2) in your Windows network settings.
Text on a website may render in a different font through Browser Isolation than it does in a local browser. This happens when the website's CSS specifies a proprietary font (for example, Arial or Times New Roman) without a generic fallback. The remote browser runs in a Linux-based environment that does not include licensed fonts typically bundled with Windows or macOS. When no matching font is found, the browser substitutes its own default.
To resolve this, add a generic fallback family (such as sans-serif or serif) to the end of the website's font-family CSS declarations. For more information, refer to Font rendering.
If a website displays incorrectly (for example, broken CSS or missing images), it may indicate that the remote browser is unable to fetch specific resources from the origin server. Check your Gateway HTTP logs for any blocked subresources that might be required by the page.
For more information, refer to the full Browser Isolation documentation.
Browser Isolation troubleshooting ❯