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This feature is currently in public preview and is not recommended for production use.
Domain filtering lets you control which external domains a sandbox can reach. You can define an allowlist (only listed domains are reachable) or a denylist (all domains except listed ones are reachable). Domain filtering and proxy routing are independent configurations — you do not need to duplicate domains across both. A domain can appear in the allowlist without having a proxy routing rule, and vice versa.
Domain filtering relies on the sandbox’s tools and libraries respecting the standard proxy environment variables (HTTP_PROXY, HTTPS_PROXY). Traffic from tools that ignore these variables will not be filtered. Routing-level enforcement is planned for a future release.

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Allowlist

Only the listed domains are reachable: 
await SandboxInstance.create({
  name: "restricted-sandbox",
  image: "blaxel/base-image:latest",
  region: "us-was-1",
  network: {
    allowedDomains: ["api.stripe.com", "api.openai.com", "*.s3.amazonaws.com"],
    proxy: { routing: [] },
  },
});

​
Denylist

All domains except the listed ones are reachable: 
await SandboxInstance.create({
  name: "denylist-sandbox",
  image: "blaxel/base-image:latest",
  region: "us-was-1",
  network: {
    forbiddenDomains: ["*.malware.com", "evil.example.org"],
    proxy: { routing: [] },
  },
});
When both allowedDomains and forbiddenDomains are set, forbiddenDomains takes precedence: a domain that appears in both lists will be blocked.

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Firewall + proxy combined

Firewall rules and proxy routing compose naturally: 
await SandboxInstance.create({
  name: "locked-down",
  network: {
    allowedDomains: ["api.stripe.com", "api.openai.com"],
    proxy: {
      routing: [
        {
          destinations: ["api.stripe.com"],
          headers: { "Authorization": "Bearer {{SECRET:stripe-key}}" },
          secrets: { "stripe-key": "sk_live_..." },
        },
      ],
    },
  },
});
Only api.stripe.com and api.openai.com are reachable. The proxy injects credentials for Stripe requests; OpenAI requests go through unmodified.
Last modified on May 28, 2026