Expose HTTP

You can run dev servers, preview apps, webhook receivers, or framework CLIs on any port and publish them instantly to a secure, random HTTPS URL.

Import the Sandbox class from the @deno/sandbox module and pass a port to the Sandbox.create() method:

import { Sandbox } from "@deno/sandbox";

await using sandbox = await Sandbox.create({ port: 8000 });
console.log(sandbox.id);

await sandbox.fs.writeTextFile(
  "main.ts",
  "export default { fetch: () => new Response('hello from a sandbox!') }",
);

const p = await sandbox.sh`deno serve --watch main.ts`.spawn();

console.log("deno now listening on", sandbox.url);

await p.output();

This can then be run by setting your Deploy token and executing:

deno run -A --watch main.ts

Setting the --watch flag allows the sandbox to restart automatically when code changes are detected, for a low-fi hot-reload experience.

The URL stays live for the sandbox lifetime, making it perfect for short-lived QA links or agent generated previews.

When to expose HTTP Jump to heading#

Expose HTTP whenever you need to share the sandbox with teammates, bots, or external services:

• Preview links for AI-generated web apps or instant demos
• Webhook receivers that must be reachable from Stripe, GitHub, etc.
• Framework dev servers (next dev, astro dev, deno task dev) that should be inspected from a browser
• Temporary APIs, health checks, or observability probes

Because sandboxes are ephemeral, you do not need to manage DNS or certificates. Each call to exposeHttp() returns a unique hostname under *.sandbox.deno.net with TLS automatically configured.

All requests to a sandbox's URL will send HTTP traffic to the sandbox.

exposeHttp() usage Jump to heading#

Sandboxes also support exposing HTTP on-demand via the exposeHttp() method:

const previewUrl = await sandbox.exposeHttp({ port: 8000 });
console.log(`Preview ready at ${previewUrl}`);

This is useful when you want to start a sandbox without HTTP exposure, then expose it later (for example, after some initialization or build steps).

Observing traffic Jump to heading#

Requests routed through the exposed URL show up alongside your Deploy logs and traces. Use the dashboard to:

• Filter logs by sandbox ID or time range
• Inspect request traces to track latency between the edge and your VM
• Cancel or restart the sandbox if a preview misbehaves

Security and networking Jump to heading#

• Exposed URLs are long, random subdomains that are hard to guess.
• TLS termination happens at the Deploy edge; traffic is encrypted end-to-end.

Cleanup and limits Jump to heading#

• An exposed URL stops accepting traffic when the sandbox lifetime ends. You can call sandbox.kill() to terminate the sandbox (and URL) ahead of schedule if needed.
• For persistent services, graduate the code into a Deploy app rather than relying on a long-running sandbox.

Full example with a framework Jump to heading#

import { Sandbox } from "@deno/sandbox";

await using sandbox = await Sandbox.create();

// Install dependencies
await sandbox.fs.writeTextFile(
  "package.json",
  JSON.stringify(
    {
      private: true,
      scripts: { dev: "next dev" },
      dependencies: {
        next: "^15.0.0",
        react: "^19.0.0",
        "react-dom": "^19.0.0",
      },
    },
    null,
    2,
  ),
);
await sandbox.fs.mkdir("pages", { recursive: true });
await sandbox.fs.writeTextFile(
  "pages/index.js",
  `export default function Home() {
  return (
    <main style={{ fontFamily: "system-ui", padding: "2rem" }}>
      <h1>Next.js sandbox</h1>
      <p>Edit pages/index.js to get started.</p>
    </main>
  );
}
`,
);
await sandbox.sh`npm install`;

// Start the dev server
const server = await sandbox.spawn("npm", {
  args: ["run", "dev"],
  stdout: "inherit",
  stderr: "inherit",
});

// Publish it
const previewUrl = await sandbox.exposeHttp({ port: 3000 });
console.log(`Preview ready at ${previewUrl}`);

await server.status; // keep running until the process exits

Using Deno Sandbox in this way allows you to spin up full-featured framework development servers with minimal code, useful for agents or developers who need to spin up high-fidelity previews, share them for feedback, and tear everything down with a single Ctrl+C.