Inside SpendSage: How We Designed a Budget App We Actually Want to Use

In my last post, I talked about why my wife, Momo, and I ended up building SpendSage: we were sick of budgeting apps that were bloated with ads, lacked shared household access, or locked basic features behind crazy paywalls.

But deciding to build an app and actually designing one that doesn't make you want to pull your hair out are two very different things.

It took us 5 months of testing, tweaking, and arguing over button placements in our living room to get SpendSage right. Here is a look under the hood at the features we built, why we built them, and how they actually work.

1. The Dashboard Hero Banner (Answering the Only Question That Matters)

When you open a budgeting app, you usually don't care about a pie chart of your last six months of grocery spending. You only care about one question: Do I have money to spend today?

We designed the Hero Banner at the very top of the dashboard to answer this instantly. It shows two numbers:

• Left to Spend: This is your everyday envelope. It takes your expected income, sets aside your fixed bills and savings, and shows you exactly what remains for the month.
• Free to Spend: This is the fun number. This is what is left over after your specific budgeted categories (like groceries or gas) have their share reserved. It is your guilt-free "treat yourself" money.

We also built a traffic-light system into it. If you blow past a budget limit, the banner doesn't pretend it didn't happen - it turns red. If you are spending too fast for the current date, it turns amber. It forces you to be honest with yourself.

2. The Monthly Planner (Because Pen and Paper Got Old)

For the first few months of testing SpendSage, Momo and I would sit at the kitchen table with the app open, writing down our budget for the next month on a physical notepad. It worked, but it was tedious.

So, we built the Monthly Planner for the web version. It is a 6-step wizard that walks you through building your next budget on purpose:

1. Add your expected income.
2. Set aside fixed bills.
3. Set your savings goals.
4. Allocate your flexible spending.
5. Divvy up anything left over.
6. Review and commit.

The best part? It remembers your history. When you plan next month, it pre-fills your categories based on your actual past spending, so you are just tweaking numbers, not starting from a blank page. And because we built this for couples, if your partner tries to edit the same plan at the same time, it warns you so you don't overwrite each other.

3. What’s Free vs. Paid (Keeping the Lights On)

I hate apps that are completely useless unless you pay. SpendSage is genuinely useful on the Free tier, while Pro exists to unlock power-user and AI features. Crucially, entitlements are tied to the household owner - so if you have Pro and invite a free user to your household, they get to enjoy the Pro features inside your shared budget.

4. iPhone Users: No App Store Required

We officially launched the Android app on the Google Play store, but iPhone users don't have to wait for an App Store release.

We built SpendSage as a Progressive Web App (PWA). This means you can install it directly to your home screen right now. It launches full-screen, hides the browser bar, and feels much like a native app.

1. Open Safari and go to spendsage.app
2. Tap the Share button (the square with the up arrow).
3. Scroll down and tap Add to Home Screen.
4. Tap Add.

That's it! The teal SpendSage icon is on your home screen and ready to go.