High-performance, Bun-optimized Excel and CSV library for TypeScript. Work with Bun S3

Github: https://github.com/vanloctech/bun-spreadsheet
NPM: https://www.npmjs.com/package/bun-spreadsheet

Why This Package

• Built for Bun, not adapted from Node-first abstractions — The core file paths use Bun.file(), Bun.write(), FileSink, and Bun-native streaming APIs directly.
• Works naturally with Bun-native file targets, including S3 — Read from and write to local paths, Bun.file(...), and Bun S3File objects, including direct streaming exports to S3 destinations.
• Production export helpers for Bun backends — Supports progress callbacks, AbortSignal, export diagnostics, streaming Response helpers, and S3 multipart tuning through Bun-native writer options.
• TypeScript-first spreadsheet model — Workbook, Worksheet, Row, Cell, and style objects are explicit and practical to work with in Bun apps.
• Focused on real report workflows — Styles, formulas, hyperlinks, data validation, conditional formatting, auto filters, freeze/split panes, and workbook metadata are supported where they matter for business exports.
• Multiple write strategies for different workloads — Use normal writes for simplicity, stream writes for lower memory pressure, and chunked disk-backed writes for large exports.

Benchmarks

Measured on Bun 1.3.10 / MacOS ARM with a single worksheet, compressed .xlsx, and 1,000,000 rows x 10 columns:

Mode	Total time	Finalize time	Rows/sec	Peak RSS	Peak heapUsed	File size
createExcelStream()	13.1s	8.9s	76,363	110.6MB	5.1MB	54.33MB
createChunkedExcelStream()	11.9s	8.5s	84,029	120.9MB	5.1MB	54.33MB

createExcelStream() now uses the same disk-backed low-memory path as the chunked writer for single-sheet exports, so the numbers are expected to be close. Re-run the large benchmark on your machine with: