How do I convert CSV to XLSX?

Add your CSV file to the upload area above, then press Convert. The XLSX file downloads straight to your device. You do not need an account, and there is no watermark.

Are my files uploaded to a server?

No. This conversion runs entirely inside your browser using WebAssembly, so the file never leaves your device — you can even disconnect from the internet after the page loads and it will still work.

Does converting to XLSX reduce quality?

Text, structure and images carry over faithfully. Exact page layout does not, because XLSX lays content out differently from CSV. Check headings, tables and page breaks in the result.

How large a file can I convert?

Up to 100 MB per file for this conversion. Because the work happens in your browser, the practical limit is your device's memory — larger files work on a desktop with plenty of RAM and may fail on an older phone.

Can I convert several files at once?

Yes. Add as many as you like and press Convert All. Each file is processed independently, so one failure does not stop the rest, and you can download everything together as a ZIP.

Can I use this on my phone?

Yes. FileTools360 works in mobile browsers on iOS and Android, including choosing files straight from your camera roll. Very large videos may run out of memory on a phone — those are better converted on a laptop.

SpreadsheetLayout rebuiltRuns in your browser

CSV to XLSX Converter

Turn CSV files into XLSX in a couple of clicks. Flat tabular text — one table, no formatting. The modern Microsoft Excel workbook format. Content is preserved and the layout is rebuilt for the target format.

On your deviceNever uploadedGone when you close the tabHow this works

Drop your files here

CSV files (.csv) · up to 100 MB each

or paste files from your clipboard

Ready when you are

Drop a CSV file above and FileTools360 will turn it into XLSX — right here on your device, without uploading anything.

⌘K to search converters

How to use it

1
Add your CSV files
Drag them onto the upload area, choose them from your device, or paste them from your clipboard. You can queue several at once.
2
Adjust the settings if you want to
The defaults suit most people. Open Advanced to control delimiter and header handling.
3
Convert and download
Press Convert. Everything happens on your own device — nothing is uploaded. Download files one by one, or grab them all as a ZIP.

CSV and XLSX explained

CSV is plain text where each line is a row and commas separate the fields. There is no formatting, no formulas, and no second sheet — which is precisely why every system on earth can read it.

XLSX is Excel's modern format — a ZIP of XML holding cells, formulas, formatting, multiple sheets, charts and pivot tables.

Where CSV files come from: Database exports, analytics tools and data interchange between systems.
Where XLSX is used: Excel, Google Sheets exports and business reporting systems.

CSV vs XLSX

The two formats solve different problems, which is why converting between them involves trade-offs rather than a straight upgrade.

CSV compared with XLSX
Property	Source	Target
Compression	None	Lossless
Introduced	—	2007
Browser support	Every spreadsheet, database and programming language.	Excel, Google Sheets, Numbers, LibreOffice.

CSV is stronger at: Readable by every spreadsheet, database and programming language. Plain text, so it diffs and streams well. Tiny files.
XLSX is stronger at: Formulas, formatting, charts and multiple sheets in one file. Compact relative to the old .xls. Supported by Excel, Sheets, Numbers and LibreOffice.

Why convert CSV to XLSX?

People make this switch when they run into the limits of CSV: the data needs formulas, formatting or multiple sheets. XLSX is the better fit when the data needs calculation, formatting or more than one sheet.

CSV limitations that prompt the switch: Exactly one table — no sheets, formatting or formulas. No type information, so leading zeros and long numbers get mangled. The 'comma' is not guaranteed; European exports often use semicolons.
What you give up: Harder to parse programmatically than CSV. Formula compatibility varies between applications.

What is preserved when converting CSV to XLSX?

Both formats store the content without discarding data, so this conversion preserves it exactly. The file size may change because the two formats compress differently, but the content itself is unaffected.

CSV has no notion of data types. A product code like 007 becomes 7 unless the importing tool is told otherwise — which is a property of CSV, not a bug in the converter.

About these formats

Source

Comma-Separated Values

Flat tabular text — one table, no formatting.

Extensions: .csv
MIME type: text/csv
Best for: Data imports and exports · Databases · Scripts
Compatibility: Every spreadsheet, database and programming language.

Target

Excel Open XML Workbook

The modern Microsoft Excel workbook format.

Extensions: .xlsx, .xlsm
MIME type: application/vnd.openxmlformats-officedocument.spreadsheetml.sheet
Best for: Multi-sheet data · Formulas · Business reporting
Compatibility: Excel, Google Sheets, Numbers, LibreOffice.

Values are type-sniffed, so numbers and dates land as real numbers and dates rather than text.

Good to know