twineconvert
Free · in-browser · no upload

XLSX to CSV
Converter

Drop your XLSX file. We'll convert it to CSV right here in your browser, your file never leaves your device.

Local

Drop your file here

or click to pick from your device

.xlsx / .xls
Nothing uploaded No file size cap Open source

How it works

Three steps. No upload, no signup.

  1. 1

    Drop your file

    Click the dropzone above or drag a XLSX from your desktop. Files of any size, there's no upload, so there's no upload limit.

  2. 2

    Convert in your browser

    The conversion runs entirely in this tab using JavaScript and WebAssembly. Your file never touches our servers, we don't have any.

  3. 3

    Download

    Get your CSV the moment the conversion finishes. Convert another, or close the tab.

Files stay on your device

Your file is never uploaded. The entire conversion runs in your browser using WebAssembly. We can't see what you convert because we have no server to see it.

No file size limit

Server converters cap free users at 1-2 GB and gate larger files behind a paid plan. Since nothing uploads, our limit is whatever your browser can handle.

Free, no signup, no ads on conversions

No account required. No watermark on the output. No queue. Open source, every line of conversion code is public.

Formats involved

About XLSX and CSV

XLSX, Microsoft Excel Spreadsheet

XLSX is the spreadsheet format Excel has used since 2007, like DOCX, it's a zip containing XML for cells, formulas, formatting, and embedded objects. Replaces the older binary .xls format. Read and written by Excel, Google Sheets, Apple Numbers, and LibreOffice Calc, with high fidelity for standard cell data and reasonable fidelity for complex formulas and pivot tables.

How to open

Microsoft Excel, Google Sheets, Apple Numbers, LibreOffice Calc. CSV is a more portable format if you only need the raw cell values.

Full XLSX format guide →
CSV, Comma-Separated Values

CSV is plain text, one row per line, fields separated by commas. The simplest possible tabular data format, which is exactly why it remains the most portable: every spreadsheet, database, programming language, and analytics tool reads CSV. Tradeoffs: no formulas, no formatting, no multiple sheets, and various edge cases around quoting fields that contain commas or newlines.

How to open

Excel, Google Sheets, Apple Numbers, LibreOffice Calc, any text editor, every database import wizard, every programming language with one line of code.

Full CSV format guide →

Related tools

Convert other files to CSV

Convert your XLSX to other formats

How we compare

XLSX → CSV vs the alternatives

FeatureUstwineconvertCloudConvertiLovePDFFreeConvertSmallpdf
Files uploaded to a server
Free file size limitNo limit1 GB200 MB1 GB5 GB
Free conversions per dayUnlimited10/dayLimitedLimited2/day
Signup required
Watermark on output
Open source
Works offline (after first load)

Last verified May 2026 from each competitor's pricing and FAQ pages. Limits and pricing change frequently.

FAQ

Common questions

Is this XLSX → CSV converter really free?

Yes. No signup, no watermark, no daily file count limit. The entire engine is open source, you can read the conversion code on GitHub.

Where does my file go when I convert it?

Nowhere. The conversion runs entirely in your browser using JavaScript and WebAssembly. Your file is never uploaded to our servers. We don't have any servers handling files, there's nothing for us to log, store, or accidentally leak.

What's the maximum file size?

Whatever your browser can hold in memory. Practically, this means a few hundred MB on most computers, significantly larger than the 1-2 GB caps that server-upload converters charge for. Very large files (multi-GB) may require closing other browser tabs first.

Why convert XLSX to CSV?

Spreadsheets with formulas, formatting, multiple sheets. Universal tabular data interchange. The most common reason to convert is compatibility, CSV works in places where XLSX doesn't, or vice versa.

How do I open a XLSX file in the first place?

Microsoft Excel, Google Sheets, Apple Numbers, LibreOffice Calc. CSV is a more portable format if you only need the raw cell values.

Does this work offline?

Once the page is loaded, the conversion itself runs entirely offline. The first time you use a tool, your browser downloads the conversion library (a one-time cache). If you reload while offline, the page won't load, but you can install the site as a Progressive Web App for full offline use.

Can I convert multiple files at once?

Single file at a time for now. Batch conversion is on the roadmap, for now, drop one file, download the result, then convert the next.