How I built a Stripe monitoring tool in my browser with zero backend

Most payment monitoring tools work the same way:
your API key goes to their server, their server
polls Stripe, their server sends you a notification.

That means your revenue data, customer patterns,
and API credentials are sitting on someone else's
infrastructure. Forever.

I built Stripe Alerts differently.

The architecture

Everything runs in the browser. Here's the full flow:

1. User pastes a read-only Stripe API key
2. Key is stored in chrome.storage.local — never synced, never transmitted
3. A Chrome Manifest V3 service worker polls the Stripe REST API directly on a schedule
4. Response is processed locally in the browser
5. Chrome's native notifications API fires the alert

The request chain is: Browser → Stripe API → Browser.
No middleman. No server. No data leakage.

Why Manifest V3 matters

Chrome's Manifest V3 forced developers to move from
persistent background pages to service workers. This
actually helped the privacy architecture — service
workers are ephemeral, they spin up to do a job and
shut down. Nothing persists in memory between checks.

What it monitors

• Failed payment spike detection
• Chargeback and dispute activity
• Subscription cancellation monitoring
• Refund anomaly detection

The result

A monitoring tool that is genuinely privacy-first by
architecture, not just by policy. There's no server
to breach, no database to leak, no API key to steal.

Free to install → https://chromewebstore.google.com/detail/stripe-alerts/epemeoabcaoifldejoblcknljpgbphao

Happy to answer any technical questions below.