Code Sandbox Unblocker — ((top))

| | Unblocker Counter | | :--- | :--- | | DNS Filtering (blocks codesandbox.io ) | Use IP address directly or VPN | | TLS SNI Inspection (sees the domain in the HTTPS handshake) | Use ECH (Encrypted Client Hello) or a forwarding proxy | | WebSocket Filtering (blocks wss:// connections) | Fallback to HTTP long-polling (rare) | | Category Blocking ("Web Tools") | Self-host a mirror on a generic domain like my-cool-project.com |

This creates a technical arms race:

with a no-logs policy (e.g., Mullvad, ProtonVPN, or Windscribe). Install it on your personal device, not a school-managed device. code sandbox unblocker

or “This category is blocked (Web Development Tools).” | | Unblocker Counter | | :--- |

(e.g., deep packet inspection detects OpenVPN), switch to Shadowsocks or V2Ray – these mimic normal HTTPS traffic. If you have no other option and accept

If you have no other option and accept the risks, here is the safest approach:

The VPN encrypts traffic, preventing the firewall from seeing the destination.