WeSplit

Singapore bill splitter: scan a receipt, tap who had what, settle with PayNow. Live at wesplit-sg.vercel.app.

Features

• Scan a receipt photo with Gemini, or type the items in. Charge modes are 10% service + 9% GST, GST only, service only, or none. When the printed total matches one of those, that mode is selected.
• Item discounts, 1-for-1 items, bill-level discounts, and an extra percentage or dollar voucher. Service charge and GST are calculated after discounts.
• Assign each item by tapping people. Portions can be uneven (for example 2:1). Shares are rounded to the cent and add up to the total.
• A PayNow QR per person, with the amount and a reference. Send it on WhatsApp or Telegram, through the share sheet, or as a saved image.
• A public link (/b/[id]) shows each person's amount and QR, follows paid status, and can be revoked. Receipt photos stay on the owner's device and in private storage.
• Bill history with place and optional location, a friends list with balances, and one PayNow nudge that covers several bills.
• Optional sign-in with Google or an email magic link. Bills, friends, PayNow details, and receipt photos then sync. Until you sign in, they stay on the device.
• Installable PWA. Entering items works offline. Light and dark theme.

Stack

• Next.js 16 (App Router), React 19, TypeScript, Node.js 22
• Vercel AI SDK (ai, @ai-sdk/google) calling Gemini
• Supabase Auth, Postgres, and Storage (@supabase/supabase-js, @supabase/ssr)
• Zod for the scan schema, qrcode for PayNow QRs
• Deployed on Vercel

The split math and PayNow payload live in lib/split.mjs. npm test runs the unit tests there.

Architecture

The UI is one client page. Bills are written to the device first. A scan posts the photo to a route handler, which asks Gemini for structured line items and then discards the image. Accounts, sync, and public links go through Supabase when those environment variables are set.

flowchart LR
  phone[Browser]
  app[Next.js app]
  scan["/api/scan"]
  gemini[Gemini]
  device[localStorage and IndexedDB]
  supa[Supabase]
  share["/b/id"]

  phone --> app
  app -->|photo| scan
  scan --> gemini
  app --> device
  app -.->|signed in| supa
  share --> supa

/api/scan checks the request origin, a short proof of work, and per-IP limits, then returns the merchant, items, discounts, and totals. PayNow QRs are built in the browser (EMVCo SGQR). Signed-in users sync bills, friends, and the PayNow profile to Postgres, and a compressed receipt photo to a private Storage bucket. Creating a share link stores a snapshot through a Supabase function; /b/[id] reads that snapshot.

Run locally

Node.js 22.

npm install
npm run dev

Open http://localhost:3000.

npm test
npm run build
npm start

Environment

Names only. Put them in .env.local, which is gitignored. Scanning and splitting need the Gemini key. Accounts, sync, and share links need both Supabase variables.

Name	Role
GOOGLE_GENERATIVE_AI_API_KEY	Gemini API key. Required to scan. Read by @ai-sdk/google.
ASK_MODEL	Optional model id. Defaults to gemini-3.5-flash-lite.
NEXT_PUBLIC_SUPABASE_URL	Supabase project URL. Accounts, sync, and share links.
NEXT_PUBLIC_SUPABASE_ANON_KEY	Supabase publishable key. Same features as the URL.

License

MIT © 2026 Josh Lim