How to Add 'Download All as ZIP' to Your SaaS in 30 Minutes

#javascript #node #tutorial #webdev

Your users uploaded 200 photos. Now they want to download them all. What do you do?

The naive approach — loop through files, zip them on your server, serve the result — falls apart fast. Memory spikes with large files. Egress fees add up. You need temp storage, cleanup jobs, and error handling for partial failures.

I hit this exact wall building a file-sharing service that's now processed 550K+ files and 10TB+ of archives. After weeks of wrestling with ZIP64, streaming, and Cloudflare Workers' 128MB memory limit, I turned my solution into an API. Here's how you can skip that pain entirely.

The 30-minute version

Step 1: Get an API key

Step 2: Collect your file URLs

You already have these — they're in your database. S3 presigned URLs, R2 public URLs, any HTTPS endpoint that returns a file.

const fileUrls = await db.query(
  'SELECT file_url, original_filename FROM uploads WHERE project_id = ?',
  [projectId]
);

Step 3: One API call

const response = await fetch('https://api.eazip.io/jobs', {
  method: 'POST',
  headers: {
    'X-API-Key': process.env.EAZIP_API_KEY,
    'Content-Type': 'application/json',
  },
  body: JSON.stringify({
    files: fileUrls.map(f => ({
      url: f.file_url,
      filename: f.original_filename,
    })),
  }),
});

const { job_id } = await response.json();

Step 4: Poll for completion and redirect

async function waitForZip(jobId) {
  const MAX_ATTEMPTS = 60;
  for (let i = 0; i < MAX_ATTEMPTS; i++) {
    const res = await fetch(\`https://api.eazip.io/jobs/\${jobId}\`, {
      headers: { 'X-API-Key': process.env.EAZIP_API_KEY },
    });
    const { job } = await res.json();

    if (job.status === 'completed') return job.download_url;
    if (job.status === 'failed') throw new Error('ZIP job failed');

    await new Promise(r => setTimeout(r, 2000)); // wait 2s
  }
  throw new Error('ZIP job timed out');
}

// In your route handler:
const downloadUrl = await waitForZip(job_id);
res.redirect(downloadUrl);

That's it. Your users click "Download All", get a ZIP a few seconds later.

What you didn't have to build

ZIP64 support — files over 4GB just work
Streaming — constant memory regardless of archive size
Error recovery — if file #500 fails, the job retries from a checkpoint
Temp storage cleanup — signed URLs expire automatically
Egress optimization — zero egress fees on Cloudflare's network

When this makes sense

SaaS with user-uploaded files — "Download all attachments" in a support ticket, bulk photo export from a gallery
E-commerce — product image packs, digital goods delivery
Internal tools — compliance teams exporting 6 months of audit logs, database backups

When it doesn't

If you only serve a handful of small files — just zip them in memory
If you need real-time streaming to the browser — this is async (job → download URL)
If you need custom compression settings — eazip uses STORE (no compression) for speed

Try it

eazip.io — free tier: 60 GB-days/month, no credit card.

Building an export feature? I'd love to hear about your use case — drop a comment or reach out.

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