How I Built a Local-First Chrome Extension to Stop Forgotten Auto-Renewals

Miguel C.G. — Thu, 20 Aug 2026 17:52:39 +0000

A few weeks ago, I got hit with a $30 automatic renewal for a subscription service I hadn't used in months. It was a classic "subscription creep" moment—a small, silent leak in my monthly budget.

When I looked for subscription tracking tools, I noticed a frustrating pattern: almost every solution required registering a cloud account, syncing sensitive bank credentials via APIs, or downloading bloated, ad-heavy mobile apps. For simply tracking a few fixed monthly renewal dates, handing over personal financial data felt like a massive privacy trade-off.

So, as a developer, I decided to build a lightweight, privacy-first tool: SubPulse.

The Architecture: 100% Local by Design
I wanted SubPulse to operate with zero server infrastructure, ensuring absolute data privacy and near-zero latency.

Privacy First (chrome.storage.local): Everything runs inside the browser storage. No backend databases, no analytics pinging external endpoints, and zero data collection.

Manifest V3 Compliant: Built entirely on modern Extension APIs for long-term browser compatibility and low memory consumption.

Frictionless Onboarding: Since there are no user accounts or OAuth flows to handle, onboarding takes under 5 seconds.

Core UI & Features
Instead of complex multi-page dashboards, I focused on high-density visual clarity:

Visual Budget Gauge: Set a custom monthly limit and immediately see spending status through a clean color-shifting progress bar (Green, Orange, Red).

Actionable Renewal Deadlines: Uses humanized timelines (like "Tomorrow" or "In 2 days") to give you actionable windows before an auto-renewal strikes.

Pausable Expenses: Easily freeze seasonal charges without cluttering active reports or losing historical data.

Shared Cost Splitter: Audit your exact personal share for group or family plans.

Tech Stack Lessons
Building an extension with a focus on local execution forced me to keep state management clean and efficient. Using chrome.storage.local means state re-renders must be reactive without relying on heavy external syncing libraries.

I'd love to hear from other extension devs: How do you balance feature density with digital minimalism in your browser extensions?

Check out the tool on the Chrome Web Store by searching for SubPulse, or drop your thoughts below!

Link to extension: https://chromewebstore.google.com/detail/subpulse-%E2%80%94-rastreador-de/oilfoalnllbibcefadnollmchomhbple?hl=es&utm_source=ext_sidebar

Thank!

DEV Community: Miguel C.G.

How I Built a Local-First Chrome Extension to Stop Forgotten Auto-Renewals