We built a Splitwise alternative where the link is the account

Description and use

Built a split‑expense app without account creation: a single link acts as invite, login, and data key, enabling ease of use, offline functionality, and privacy.

Problem

Users would not create accounts, so the product needed to be accessed via a single link that served as invite, login, and data key.

Outcome

A fully functional split‑expense app that requires no account creation, supports offline usage, and maintains privacy and security through a single link bearer credential.

Workflow

• Generate a 16‑byte random key, base64url‑encode it, and append to a readable URL stem.
• Use the link as a bearer credential; no recovery or owner override. Use BigInt for money amounts; display as strings. Lock FX rates at entry; never re‑price history. Queue new expenses offline and replay when online. Use SSE to notify clients of changes; clients refetch data. Route all external requests through an allow‑listed proxy to avoid egress from containers.

Evidence

The link is a bearer credential. 16 random bytes, base64url, appended to a readable stem. No recovery, no owner override. Treat it like a key.

Source

Money as strings + BigInt. A Number never touches an amount except for display.

Source