How I Built a Privacy-First Subscription Tracker as a Chrome Extension

SubPulse — Sun, 27 Sep 2026 18:45:49 +0000

I built SubPulse because I wanted a simple way to keep track of subscriptions without connecting my bank account or giving a service access to my emails.

It's a Chrome extension that helps you track recurring subscriptions, upcoming renewals and spending.

But the interesting part wasn't just building another subscription tracker.

It was figuring out how to build one that stays useful while keeping the architecture as simple and privacy-focused as possible.

The idea

Most subscription trackers can become quite complicated.

Accounts, financial connections, email scanning, cloud databases, integrations...

I wanted to take a different approach.

With SubPulse:

No account is required
No bank connection
No email scraping
No server storing your subscription list
Subscription data stays in the browser

The trade-off is that users add their subscriptions manually.

That makes the initial setup less automatic, but it also means I don't need access to someone's financial data just to tell them when Netflix is renewing.

Building it as a Chrome extension

The extension is essentially a small personal dashboard that lives inside Chrome.

The core data model is relatively simple:

A subscription contains things like:

Name
Price
Currency
Billing frequency
Next renewal date
Category
Status

From that data, SubPulse can calculate things such as monthly spending, upcoming payments and category breakdowns.

The interesting part is that a relatively small amount of structured data can produce quite a lot of useful information.

Notifications

One of the main reasons I built SubPulse was to solve a very specific problem:

You sign up for something, forget about it, and then get charged weeks or months later.

So renewal reminders became one of the most important parts of the product.

SubPulse can send Chrome notifications before a subscription renews, and the extension can also show upcoming or overdue renewals through its Chrome badge.

The goal is simple:

Don't make people remember their subscriptions.

Let the tool remember for them.

Spending and upcoming payments

Once you know the subscriptions and renewal dates, you can do more than just send reminders.

SubPulse also calculates:

Monthly subscription spending
Spending by category
Spending history
Upcoming payments
Month-to-month spending changes
Progress towards a custom monthly spending limit

This is where I started thinking about SubPulse less as a reminder tool and more as a small personal subscription dashboard.

Supporting multiple currencies

Another problem I wanted to solve was having subscriptions in different currencies.

For example, someone might have:

One subscription in EUR
Another in USD
Another in GBP

SubPulse supports multiple currencies and converts them for the spending overview while keeping the original currency for each subscription.

There is also an offline-rate warning when current exchange-rate data isn't available.

Backup without an account

Because the data stays locally in the browser, I still wanted users to have a way to protect their data.

So I added backup and import functionality.

Users can export their subscriptions and settings to a file and import them again later.

This means the product doesn't need a traditional account system just to provide basic data portability.

What I've learned so far

The product is now at version 1.2.5.

I've added quite a few things since the first version:

Renewal notifications
Upcoming payments
Spending history and trends
Multiple currencies
Budget limits
Calendar export
CSV export
Backup/import
Search and filtering
Pause/resume subscriptions
Dark/light/automatic themes
English and Spanish
Weekly renewal summaries for Pro users

But probably the biggest thing I've learned isn't technical.

It's that building features and getting people to use them are two completely different problems.

After around 90 days, SubPulse has:

89 downloads
34 users
9 uninstalls
225 Chrome Web Store impressions

Those numbers are still small, but they're enough to start asking better questions.

The next problem: retention

Now I'm trying to understand what actually makes someone come back after adding their subscriptions.

Is it:

A renewal reminder?
Checking upcoming payments?
Looking at spending?
Seeing that a subscription increased in price?
Checking a monthly spending limit?

I don't know yet.

And I don't want to guess.

So my next step is to focus less on adding features and more on understanding user behavior.

I'm particularly interested in tracking the journey from:

install → first subscription → first reminder → return

I'd also like to talk to users directly and understand why they opened the extension again — or why they didn't.

What's next

For now, I'm focusing on improving the existing product rather than adding features endlessly.

I want to understand:

Why people install SubPulse
What makes them add their subscriptions
What makes them come back
What eventually makes someone pay for Pro

I'm also sharing the journey across different platforms and trying to learn what actually works for getting the first users.

If you're building a Chrome extension, SaaS or another small product, I'd love to hear:

What was the hardest part for you after getting your first users — acquisition, activation, retention or monetization?

And if you'd like to see SubPulse, I'll leave the link below.

SubPulse: https://subpulseapp.netlify.app/

DEV Community: SubPulse