---
title: Server upload route
description: A route that takes a file from the browser, converts it with your key, and returns signed output URLs.
---

This route sits between your web app and convt so the API key stays on the server. It uses the standard `Request` and `Response` objects, so the same handler runs on Bun, Deno, Node 20+ frameworks, Cloudflare Workers and Next.js route handlers. It imports `convert` and `formatFor` from the [Node helper](/docs/examples/node-script).

```js server.mjs lineNumbers
import { convert, formatFor } from "./convt.mjs";

const MAX_BYTES = 50 * 1024 * 1024; // your limit, below convt's 2 GB
const TARGETS = new Set(["webp", "png", "jpeg", "pdf"]);

export async function handleConvert(request) {
  // Authenticate your own user here before spending your convt budget.

  const form = await request.formData();
  const file = form.get("file");
  const to = String(form.get("to") ?? "");
  if (!(file instanceof File)) return new Response("file is required", { status: 400 });
  if (!TARGETS.has(to)) return new Response("unsupported target", { status: 400 });
  if (file.size === 0 || file.size > MAX_BYTES)
    return new Response("file too large", { status: 413 });

  try {
    const outputs = await convert({
      bytes: new Uint8Array(await file.arrayBuffer()),
      from: await formatFor(file.name),
      to,
    });
    return Response.json({ outputs });
  } catch (error) {
    console.error(error);
    return new Response(error.message, { status: 502 });
  }
}

// Bun: bun server.mjs
if (typeof Bun !== "undefined") {
  Bun.serve({
    port: 3000,
    fetch: (request) =>
      new URL(request.url).pathname === "/api/convert" && request.method === "POST"
        ? handleConvert(request)
        : new Response("not found", { status: 404 }),
  });
}
```

The browser side is the form from the [Quick start](/docs/quick-start?client=browser):

```js
const body = new FormData();
body.append("file", fileInput.files[0]);
body.append("to", "webp");
const res = await fetch("/api/convert", { method: "POST", body });
const { outputs } = await res.json();
link.href = outputs[0].url;
```

The signed URLs expire after 5 minutes. To let users download later, store the job id and call `GET /v1/jobs/{id}/download` for fresh URLs when they click, any time in the 24 hours before the job expires.

[Browser apps](/docs/guides/browser-apps) explains why the upload goes through your server.