---
title: Deno Deploy
description: Wrap any Deno fetch handler with createAEOHandler for edge negotiation.
---

`@dualmark/deno` is a higher-order Deno handler. Pass it your existing `Deno.serve` fetch handler (or a thin static-file reader), and it adds AI bot detection, markdown serving, header injection, and lifecycle hooks for telemetry -- all using standard WHATWG Fetch primitives.

## Install

`@dualmark/deno` is published to npm but exports the `"deno"` condition first, so you can pull it in via npm specifiers in `deno.json`:

```jsonc title="deno.json"
{
  "imports": {
    "@dualmark/deno": "npm:@dualmark/deno@^0.1.0",
    "@dualmark/core": "npm:@dualmark/core@^0.7.0"
  }
}
```

For local tooling and tests under Node or Bun, install from npm directly:

<Tabs items={["bun", "npm", "yarn"]}>
<Tab value="bun">
```bash
bun add @dualmark/deno @dualmark/core
```
</Tab>
<Tab value="npm">
```bash
npm install @dualmark/deno @dualmark/core
```
</Tab>
<Tab value="yarn">
```bash
yarn add @dualmark/deno @dualmark/core
```
</Tab>
</Tabs>

## Static site (file-based content)

```ts title="main.ts"
import { createAEOHandler } from "@dualmark/deno";

const upstream = async (req: Request): Promise<Response> => {
  const url = new URL(req.url);
  let pathname = url.pathname === "/" ? "/index" : url.pathname;

  if (pathname.includes("..")) {
    return new Response("Forbidden", { status: 403 });
  }

  const hasExtension = /\.[a-z0-9]+$/i.test(pathname);
  const filePath = hasExtension ? `./content${pathname}` : `./content${pathname}.html`;

  try {
    const body = await Deno.readTextFile(filePath);
    const contentType = filePath.endsWith(".md")
      ? "text/markdown; charset=utf-8"
      : "text/html; charset=utf-8";
    return new Response(body, { headers: { "content-type": contentType } });
  } catch {
    return new Response("Not Found", { status: 404 });
  }
};

Deno.serve(createAEOHandler({ upstream }));
```

Run with:

```bash
deno run --allow-read --allow-net main.ts
```

## Wrapping an existing fetch handler

```ts title="main.ts"
import { createAEOHandler } from "@dualmark/deno";
import myApp from "./app.ts";

Deno.serve(createAEOHandler({
  upstream: myApp.fetch,
  redirects: {
    internal: { "/old-path": "/new-path" },
    external: { "/login": "https://app.example.com" },
  },
  hooks: {
    onAIRequest: (info) => console.log(`${info.botName} hit ${info.pathname}`),
    onMiss: (info) => console.warn(`miss: ${info.pathname}`),
  },
}));
```

## Verify

The example at `examples/deno-deploy` scores a perfect **125/125** under `deno run`:

```bash
deno task dev
# new terminal:
bunx @dualmark/cli verify http://localhost:8000/pricing
```

## What it does

1. **Trailing slash enforcement** -- configurable: `never` (default), `always`, `preserve`
2. **AI bot detection** -- via UA, against the registry of [known crawlers](/docs/spec/ai-bot-detection)
3. **Content negotiation** -- via Accept header, RFC 7231 §5.3.2 compliant
4. **Markdown serving** -- delegates to your `upstream` for the `.md` twin, decorates with full AEO headers
5. **Internal redirects** -- routes to target's `.md` with `X-Redirect-From` / `X-Redirect-To`
6. **External redirects** -- returns markdown notice with target link
7. **406 fallback** -- when neither HTML nor markdown is acceptable
8. **Link header injection** -- `<...>; rel="alternate"; type="text/markdown"` on HTML responses
9. **Lifecycle hooks** -- `onAIRequest` and `onMiss` scheduled on `info.completed` (Deno Deploy's equivalent of `ctx.waitUntil`)
10. **Safe-method gating** -- only `GET` and `HEAD` are intercepted; `POST`/`PUT`/`DELETE` pass through unchanged
11. **Pass-through** -- falls through to upstream for skip-prefixed paths, static assets, and everything else

## Differences from `@dualmark/cloudflare`

| Concept | Cloudflare Workers | Deno Deploy |
| --- | --- | --- |
| Static assets | `env.ASSETS.fetch()` binding | User-provided `upstream(req, info)` callback |
| Background work | `ctx.waitUntil(promise)` | `info.completed.then(promise)` |
| Built-in analytics | `AnalyticsEngineDataset` | **Not provided** -- use the `onAIRequest` hook with the telemetry of your choice |
| Geo data | `cf-ipcountry` header | Standard `x-forwarded-for` / `info.remoteAddr.hostname` |