splitlens

Inspiration

this was built after a trip and i was having a hard time in calculating the total expenses and didn't want to do it after every trip so i built this.

What it does

it takes in your credit card statement and split wise csv and calculates total how much spent, where and still how much i am owed

How we built it

Next.js 14, Supabase, and Groq's Llama 3.3 to parse bank statement PDFs into categorized transactions automatically. Shared expenses run as a separate rolling ledger with a contacts system that doesn't require friends to have accounts.

Challenges we ran into

Gemini's free tier died mid-build from debugging, forcing a pivot to Groq. Figuring out how shared expenses should interact with personal budgets without inflating your spend took more iteration than any code problem.

Accomplishments that we're proud of

The full loop works — upload a PDF, get a categorized month of spending in seconds, zero manual entry. Plus a one-click Splitwise CSV importer to migrate existing expense history.

What we learned

Always have a fallback AI model ready. The hardest problems were product decisions, not technical ones.

What's next for splitlens

Splitwise API for full split history, Plaid for automatic imports, and a mobile app — since expense tracking is fundamentally a phone-first habit.

Built With

• next.js
• supabase
• typescript