Delivering Digital Files Without a Backend

I recently built a small marketplace for texture packs for designers. The goal was simple: sell files instantly after payment, without setting up a Node.js server, writing API routes, or dealing with complex databases.

If you want to deliver zip files, PDFs, or code snippets automatically, you don't need a backend. You can do this entirely from your frontend or serverless functions by leveraging the way HTTP responses work.

Here is the practical reality of how to make this happen.

The Core Concept: Custom Content Disposition

When a user requests a file, your server sends back binary data. By default, browsers try to render that data as HTML, CSS, or text. To force a browser to download the file instead of opening it, you need to change the Content-Disposition header.

This header tells the client: "Don't display this, save it to disk."

In a standard Node.js server, this is how you set it up. You tell the system that the response is a "attachment" (download) and name the file whatever you want.

// Express.js example
res.setHeader('Content-Disposition', 'attachment; filename=my-assets.zip');
res.sendFile('/path/to/file.zip');

This is the foundation of the entire operation. The file still exists on your server, but the "handling" logic happens without a backend API to process the payment logic first.

Connecting the Payment Gateway

You cannot rely solely on a static link because you cannot monetize a static link. You need a transaction trigger.

The industry standard for this is Stripe. Stripe handles the payment, security, and webhook events.

1. Create a product in Stripe (e.g., "UI Kit").
2. Generate a checkout link using Stripe API.
3. Include the URL of your file as a "success_url" parameter.

When the user completes the payment, Stripe redirects them to your success page.

This creates a dependency problem: your server doesn't know if the user actually paid unless you poll Stripe's API or listen to a webhook. Since we are doing this without a backend, we rely on a client-side trigger.

The Frontend Logic (Client-Side Fetch)

You need a way to verify the payment from the user's browser.

This approach works best if you use a webhook for verification on the server side, but for a "no backend" implementation, you can use Stripe's API client in the browser.

You ask Stripe if this session ID is paid. If it is, you fetch the file.

Step 1: Verify Payment Status

const stripe = Stripe('YOUR_PUBLIC_KEY');
const session = await stripe.checkout.sessions.retrieve(sessionId);

if (session.payment_status === 'paid') {
    // Proceed
}

Step 2: Fetch the File
Once you have confirmed payment, you use the browser's fetch API to grab the binary data.

const response = await fetch('https://your-domain.com/dl/file.zip');
const blob = await response.blob();

// Create a temporary link to trigger download
const link = document.createElement('a');
link.href = window.URL.createObjectURL(blob);
link.download = 'my-assets.zip';
link.click();

This approach is fully client-side. It requires no server-to-server communication for the file transfer, making it incredibly cheap and fast.

Handling Security and Permissions

The biggest risk here is that if the download link is guessable, anyone can get the file for free.

You must obscure the download URL.

1. Hash the file path: Instead of files/asset.zip, use a random hash like files/a1b2c3d4.zip.
2. Map hash to ID: On your server (or a static site generator like Hugo), create a mapping file. This is just a JSON object: { "a1b2c3d4": "file.zip" }.
3. Serve the JSON: When a user requests a hash, you read the JSON to find the real filename.
4. Deliver the File: If the hash exists and the user has paid, serve the real file with the Content-Disposition header.

If someone guesses the hash, they only get an error or a 404. They cannot find the file.

Static Site Considerations

If you are building this on a platform like Netlify or Vercel, you can achieve this by configuring your netlify.toml file.

You can set up a rewrite rule that intercepts requests to /dl/*. This rule points to a function that serves the file based on the request parameter. Because Vercel/Netlify Functions are serverless, you still have access to the res.setHeader logic discussed earlier.

This keeps your infrastructure costs at zero while maintaining the security of a dynamic system.

The Result

You now have a system where:

• Stripe handles the money.
• A client-side script verifies the payment.
• A browser fetch delivers the binary blob.
• A serverless function serves the file with the correct headers.

This method is robust enough for thousands of micro-transactions and requires zero maintenance of a database. It moves the complexity from your backend to the frontend layer, where the browser handles the heavy lifting.

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