A collaborative receipt splitter built with Next.js, React, TypeScript, and Yjs. Room data is persisted locally with IndexedDB and synchronized between peers with WebRTC by default, with optional Liveblocks-hosted synchronization.
To use Liveblocks-hosted Yjs synchronization and persistence instead of WebRTC, set NEXT_PUBLIC_LIVEBLOCKS_PUBLIC_KEY to a Liveblocks public API key before building or running the app. No application backend is needed; without this setting, the app keeps using its existing P2P sync.
Public-key mode is client-only and does not authenticate users or restrict access to individual rooms. New room links use a random UUID encoded in the URL to make rooms difficult to discover, but this is obfuscation—not authorization or encryption. Anyone who obtains a room link can access its data. Use it only for non-sensitive receipts; private rooms require Liveblocks token authentication through a trusted backend.
npm install
npm run dev
npm test
npm run buildRun locally with npm run dev, build with npm run build, and serve the production build with npm start. The tests run with npm test.
Vercel auto-detects Next.js; use its default build command and output with no vercel.json or SPA rewrites. The app uses Next.js's default server/hybrid deployment, and its single route is statically prerendered. Configure NEXT_PUBLIC_LIVEBLOCKS_PUBLIC_KEY in the Vercel Preview and Production environments only if using Liveblocks; it is client-exposed. WebRTC signaling uses the existing public signaling servers and needs no environment variable. Room and ingest URL fragments and query parameters are handled client-side.
Room IDs use the urn:split:room:<uuid> format and are base64url-encoded in the URL; existing links with legacy room IDs remain supported. Receipt seeds can be shared as compressed URL hash parameters. Claims are stored as flat itemId::participantId values in Yjs so independently hydrated rooms can merge claims without replacing nested item data.
Each receipt room stores an ISO 4217 currency (default USD, so legacy rooms and links without one open as USD). It is synced through Yjs and included in receipt seeds. Amounts are formatted with Intl.NumberFormat, and splitting is done in integer minor units using the currency's exponent (JPY 0, USD 2, KWD 3), with remainders distributed deterministically so shares add up exactly. New blank rooms default to the locale's currency.
Optionally choose a display currency in the edit drawer to see each share converted. Rates come from Frankfurter (ECB data, no API key) fetched client-side and cached in IndexedDB; the rate and its date are stored on the receipt so all peers see identical values. Offline, with no cached or stored rate, amounts show in the receipt currency only. The rate can also be edited manually.