New challenge: Build an expense splitter app

We've launched a new premium challenge: an expense splitter for groups. You'll build the kind of app friends reach for after a trip or a shared dinner, where everyone logs what they paid, splits it fairly, and sees who owes whom. It's a product challenge, so there's no Figma file. The design decisions are yours, and you'll deploy the finished app to a live URL that anyone can use.

What you'll build

A shared expense tool for groups: roommates, trip companions, friend groups. The heart of the app is the money math, and there's plenty of real-world nuance to get right:

• Groups with members, including people who don't have an account
• Expenses split equally, by exact amounts, by percentages, or by shares
• Multi-currency support with live exchange rates, converted to each group's default currency
• Balances that show who owes whom, with pairwise settlement suggestions
• Categories, filtering, and a spending breakdown
• A landing page and a guest experience that lets anyone explore without signing up

What's included

There's no Figma file for this one, but the starter code gives you a full brief to build from:

• A complete spec: product definition, core and stretch features, and the technical requirements
• A brand kit with colors, typography, and spacing, plus starter CSS tokens and an optional Tailwind config
• Sample data (5 groups, 43 expenses) that seeds the guest experience, with realistic edge cases baked in
• AGENTS.md and CLAUDE.md files so AI tools have full project context from your first prompt

Two ways to build it

The recommended path is full-stack: a real database, authentication, and the currency API behind a deployed app. If you'd rather focus on the frontend, there's a frontend-only path that swaps the database and auth for local storage and a single-user app. The currency API integration and all the split, balance, and settlement logic stay the same either way.

What you'll practice

This is a Guru-level project, and it stretches the skills a strong portfolio piece should show:

• Modeling group expenses, split types, and multi-currency balances correctly
• Integrating a live external API with caching and sensible error handling
• Handling real financial edge cases: rounding, currency conversion, and settlement math
• Making genuine product and design decisions, and documenting your reasoning
• Collaborating with AI across planning, building, and polishing

How to start

Head to the challenge page, download the starter code, and read through the README. It points you to the spec, the brand kit, and the sample data. These challenges are designed for AI collaboration, so lean on AI across planning, building, and polishing. The product and design decisions are still yours to make, and that's where the real value is.

Ship something real

Because you deploy this to a live URL, it's a working product that you, your friends, and your family can use to split a real trip or a shared flat. That matters for your portfolio: a project real people use tells a much stronger story than another demo app. The guest experience is what makes that work. Anyone who clicks your link sees the product running in seconds, with no sign-up wall in the way.

Some ideas to test yourself

Once the core app works, here are a few ways to push it further:

• Visualize spending with interactive charts, over time and by category
• Add a debt-simplification algorithm that settles everyone in the fewest payments
• Suggest descriptions, categories, and splits from past expenses
• Scan a receipt photo with AI to auto-fill an expense
• Make it an installable PWA that works offline

Join the community

Building alongside other people makes a real difference. Share your progress in our Discord community, ask for feedback, and see how others approached the same spec. We'd love to see what you ship.

If you enjoy this one, our other product challenges go further into full-stack builds and real APIs. Whatever you pick next, we hope you're enjoying building real products with us.

Happy coding!