ethercalc

EtherCalc is an open-source, real-time collaborative spreadsheet server built as a Node.js port of SocialCalc, designed for teams and developers who need a lightweight, self-hosted alternative to Google Sheets. It allows multiple users to edit the same spreadsheet simultaneously in a web browser, with data stored on the server. Its interest lies in combining the simplicity of a classic spreadsheet with real-time collaboration and full control over data privacy, all in a minimal, hackable package.