I built SplitterUp because Splitwise annoyed me and I had time on my hands. That's really it.
The Frustration
Like millions of others, I've used Splitwise for years. It works. But every time I opened it, something felt off. The UI was clunky and confusing, with workflows that seemed to fight against iOS design conventions rather than embrace them. It never felt native. It felt like a web app grudgingly squeezed into a mobile shell.
I watched friends and family struggle with it too. Even experienced users would pause mid-expense, confused about where to tap next. Settling up with a large group was an exercise in patience. For an app that's supposed to reduce friction around money, there was an awful lot of friction.
But I kept using it. What else was there?
The Timing
Earlier this year, I spent months as the lead engineer on a massive project at work. Complex, technically challenging, the kind of thing you throw yourself into completely. We were about to launch when the company did layoffs and shelved the whole thing.
That sucked. But the aftermath was worse—five months of no major projects, no direction. I got bored.
My wife and I travel a lot and go out with friends constantly. We'd manually track payments in a notes app because I hated Splitwise's UI that much. (And who wants to pay $5/month just to actually use the thing?) Eventually I thought: I could build something better.
I had the time. I had a problem worth solving. Why not?
The Build
I'd never built a mobile app. My background is backend systems and enterprise architecture. I'd only dabbled in React Native. Frontend work always felt tedious to me, even though I know what good design looks like.
Turns out building something production-ready takes all 20 years of experience. Database design for scale, edge case planning, learning React Native properly while integrating native iOS features (Apple Vision for receipt scanning, on-device Foundation models for parsing). Social auth, onboarding flows, multi-currency support. Complex stuff like auto-resplitting balances when someone new joins a group.
The UX was harder than I expected. Bill splitting sounds simple until you deal with changing group membership, partial payments, friend requests, notifications, settlement calculations across dozens of expenses. Making all that feel intuitive took work.
Claude Code was huge for this. I could prototype UI ideas quickly without the usual frontend grind. That changed everything for me.
One Month Later
Thirty days. That's how long it took to get to an App Store-ready build with most of what Splitwise does. (For context: they have ~50 employees, $30M in funding, and 15 years on me.)
The app ended up at 17 feature modules and 185k+ lines of code. I'm extremely proud of it.
Steve Jobs' father once told him that when building a fence, you make the back that people won't see just as beautiful as the front, like a great carpenter would make the back of a chest of drawers. Even though others won't see it, you'll know it's there, and that will make you more proud of your design. That's stuck with me. The details nobody notices matter just as much as the ones they do.
In SplitterUp, that means smooth animations, thoughtful error states, edge cases handled gracefully. It means the app doesn't crash when you lose signal mid-sync. It means the settlement algorithm is actually correct, not just close enough. It means font sizes, layouts, colors, spacing between elements all feel right. It means your data is encrypted and I genuinely don't have access to it, not because I have to say that, but because that's how it should be built.
Even "boring" apps should be fun to use. The little details add up.
Of course it's not "done." I'm still tweaking things, adding features, working on the iPad layout. Maybe a macOS version eventually. But that's the fun part. I like having something to tinker with.
SplitterUp has the basics you'd expect: receipt scanning, flexible splitting, real-time sync, payment integration. But it also feels like it belongs on an iPhone, which Splitwise never did. The workflows make sense. Settlements don't require a PhD.
What's Next
SplitterUp launches on iOS first, with Android coming after. You can follow along at splitterup.app.
Not sure what I'll build next under All Day Software, but it'll be the same approach: no shortcuts, privacy-first, actually useful.
If you've ever been annoyed by Splitwise, this one's for you.