DEV Community: Loc Nguyen

Read and Write Excel Files in Bun with bun-excel

Loc Nguyen — Sat, 06 Jun 2026 04:21:24 +0000

If you are building a Bun app and need to export Excel or CSV files, bun-excel provides a Bun-native API for common spreadsheet workflows.

It supports .xlsx, CSV, styles, formulas, hyperlinks, streaming exports, and Bun file targets such as local files, Bun.file(), and S3File.

Install

bun add bun-excel

Write an Excel file

import { writeExcel, type Workbook } from "bun-excel";

const workbook: Workbook = {
  worksheets: [
    {
      name: "Report",
      columns: [{ width: 20 }, { width: 12 }],
      rows: [
        {
          cells: [
            { value: "Name", style: { font: { bold: true } } },
            { value: "Score", style: { font: { bold: true } } },
          ],
        },
        { cells: [{ value: "Alice" }, { value: 95 }] },
        { cells: [{ value: "Bob" }, { value: 87 }] },
      ],
    },
  ],
};

await writeExcel("report.xlsx", workbook);

Read it back

import { readExcel } from "bun-excel";

const workbook = await readExcel("report.xlsx");

for (const sheet of workbook.worksheets) {
  for (const row of sheet.rows) {
    console.log(row.cells.map((cell) => cell.value).join(" | "));
  }
}

Stream large exports

For large reports, you can write rows incrementally:

import { createExcelStream } from "bun-excel";

const stream = createExcelStream("large-report.xlsx", {
  sheetName: "Data",
  columns: [{ width: 10 }, { width: 30 }, { width: 15 }],
});

stream.writeRow(["ID", "Product", "Price"]);

for (let i = 0; i < 100_000; i++) {
  stream.writeRow([i + 1, `Product ${i + 1}`, Math.random() * 1000]);
}

await stream.end();

CSV support

import { writeCSV, readCSV } from "bun-excel";

await writeCSV("users.csv", [
  ["Name", "Age"],
  ["Alice", 28],
  ["Bob", 31],
]);

const rows = await readCSV("users.csv");

When to use it

Use bun-excel when you need spreadsheet exports in a Bun backend, especially for reports, admin tools, dashboards, or data pipelines.

Package: https://www.npmjs.com/package/bun-excel

GitHub: https://github.com/vanloctech/bun-excel

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

Loc Nguyen — Tue, 17 Mar 2026 03:36:05 +0000

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

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:

[Open Source] yt-dlp GUI with a beautiful interface and full features, support 1800+ websites.

Loc Nguyen — Wed, 21 Jan 2026 17:27:45 +0000

A modern, beautiful YouTube video downloader built with Tauri and React

Download Latest Release: https://github.com/vanloctech/youwee/releases/latest

Source Code: https://github.com/vanloctech/youwee

Report a Bug: Please use the "Bug Report" flair or open an issue on GitHub.

Features

Batch Downloads - Download multiple videos at once
Playlist Support - Download entire YouTube playlists
Multiple Quality Options - From 360p to 4K Ultra HD
Subtitle Support - Ability to embed subtitles into videos or save them as separate files.
Batch Downloading - Support for downloading multiple videos simultaneously.
Expanded Compatibility - Added support for 1800+ websites powered by yt-dlp.
Download Management - Added Download History and Library sections.
8K Resolution Support - High-quality video downloading now supports up to 8K resolution.
Developer Tools - Added access to yt-dlp logs and execution commands for debugging.
Audio Extraction - Extract audio in MP3, M4A, or Opus formats
6 Beautiful Themes - Midnight, Aurora, Sunset, Ocean, Forest, Candy
Dark/Light Mode - Choose your preferred appearance
H.264 Codec - Maximum compatibility with all players
File Size Estimation - Know the size before downloading
Fast & Lightweight - Built with Tauri for minimal resource usage
No External Dependencies - yt-dlp bundled with the app