The XLSX library your bundler will thank you for. Zero dependencies. Fully async. Works in Node.js and the browser.

Documentation | API Reference

npm install xlsx-format

import { readFile, writeFile } from "node:fs/promises";
import { read, write, sheetToJson, jsonToSheet, createWorkbook } from "xlsx-format";

// Read an Excel file into JSON
const workbook = await read(await readFile("report.xlsx"));
const rows = sheetToJson(workbook.Sheets[workbook.SheetNames[0]]);

// Write JSON back to Excel
const sheet = jsonToSheet([
	{ Name: "Alice", Revenue: 48000 },
	{ Name: "Bob", Revenue: 52000 },
]);
await writeFile("output.xlsx", await write(createWorkbook(sheet, "Q4 Sales")));

Most projects just need XLSX -- but the popular libraries ship with support for dozens of legacy formats, pull in 7-9 runtime dependencies, and lock you into synchronous APIs that block the event loop.

xlsx-format does one thing well: read and write modern Excel files. The result is a library you can actually tree-shake, await, and ship to the browser without a separate bundle.

For a detailed feature matrix (cell data, formulas, styles, comments, hyperlinks, and more), see Why xlsx-format? in the docs.

xlsx-format is fully platform-agnostic -- it never imports node:fs or any other Node.js built-in. This means it works out of the box in browsers, edge runtimes (Cloudflare Workers, Deno Deploy), and Node.js without bundler polyfills.

Node.js -- Pair read() / write() with Node's fs module:

import { readFile, writeFile } from "node:fs/promises";
import { read, write } from "xlsx-format";

const wb = await read(await readFile("input.xlsx"));
await writeFile("output.xlsx", await write(wb));

Browsers -- Use the File API or fetch:

import { read, write } from "xlsx-format";

// Read from a file input
const wb = await read(await file.arrayBuffer());

// Trigger a download
const blob = new Blob([await write(wb, { type: "array" })], {
	type: "application/vnd.openxmlformats-officedocument.spreadsheetml.sheet",
});
const link = document.createElement("a");
link.href = URL.createObjectURL(blob);
link.download = "output.xlsx";
link.click();

The API is intentionally close to SheetJS. Three things change:

1. read() and write() are async (ZIP uses streaming)
2. Named imports replace the namespace: import { read } from "xlsx-format"
3. Utility names are camelCase: sheetToJson instead of XLSX.utils.sheet_to_json

- import XLSX from "xlsx";
+ import { read, write, sheetToJson, sheetToCsv } from "xlsx-format";

- const wb = XLSX.read(buffer);
+ const wb = await read(buffer);

- const rows = XLSX.utils.sheet_to_json(ws);
+ const rows = sheetToJson(ws);

- const buf = XLSX.write(wb, { type: "buffer", bookType: "xlsx" });
+ const buf = await write(wb, { type: "buffer" });

Cell objects keep the same shape: { t: "n", v: 42, w: "42" } works exactly as before. For a full function mapping table, see the Migration Guide.

Based on the work of SheetJS, originally created by SheetJS LLC. Thank you to the SheetJS team and its contributors for building the foundation this library stands on.

Apache 2.0 -- see LICENSE for details.

Copyright (C) 2012-present SheetJS LLC (original work)

Open Source at Sebastian Software
Copyright © 2025–2026 Sebastian Software GmbH