SimpleSpread is an open-source native macOS spreadsheet application written entirely in Swift. It uses XLSX as its native file format and supports CSV import and export, with a spreadsheet model, formula engine, XLSX/ZIP/CSV I/O, and grid implemented from scratch rather than through third-party libraries.
The app is designed for working with conventional spreadsheets as well as analysis workflows. It includes documented support for 157 functions, Excel-style editing behavior, and pivot tables that can be created, refreshed, and saved in files shared with Excel. The repository also provides build, test, release, and update documentation for users and contributors.