SpreadsheetLayout rebuiltRuns in your browser

CSV to Excel (XLS) Converter

Turn CSV files into Excel documents in a couple of clicks — the file you get is a .xls, which is what Excel saves and opens. Flat tabular text — one table, no formatting. Content is preserved and the layout is rebuilt for the target format.

Not uploaded to any serverConverted on this deviceGone 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 XLS — 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 drop area, choose them from your device, or paste them from your clipboard. You can queue several at once. Nothing is sent anywhere — the file stays on this device.
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.

Privacy, in plain words

Is it safe? Your CSV file is not uploaded anywhere

What “uploaded” normally means. On most online converters, pressing the button copies your file across the internet onto a computer owned by that website. That copy is what the word “upload” means, and it is the part nobody explains.

What happens instead. This site does not do it. There is no server here that receives files, so your CSV file is read, converted and handed back by the browser you are using right now. It never travels — so there is no copy to store, read, leak or hand over.

Check it yourself in ten seconds

Turn off your Wi-Fi after this page has loaded, then convert a file anyway. It still works, because everything needed is already on your device.

The longer explanation of how this works, and the full detail of what is and is not stored on the privacy page.

Why this matters more than it sounds

A spreadsheet is rarely about one person. It is usually about hundreds of them, which is what turns an ordinary file into a reportable data breach. It matters more than it sounds, because of what spreadsheets usually are:

Customer and member lists

names, emails, phone numbers, addresses

Patient or client records

regulated personal data under HIPAA, GDPR and similar

Financial models and forecasts

numbers a competitor would pay for

Supplier pricing

commercially confidential by contract, usually

A file that is never sent cannot be kept, leaked, subpoenaed or used to train anything. That is a property of how this works, not a promise about how carefully it is run.

CSV and XLS 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.

The pre-2007 Excel format is a binary structure limited to 65,536 rows and 256 columns — limits modern datasets routinely exceed.

Where CSV files come from: Database exports, analytics tools and data interchange between systems.
Where XLS is used: Spreadsheets from Excel 2003 or earlier, and some legacy export systems.

CSV vs XLS

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

CSV compared with XLS
Property	Source	Target
Compression	None	None
Introduced	—	1987
Browser support	Every spreadsheet, database and programming language.	Still opens in Excel and LibreOffice.

CSV is stronger at: Readable by every spreadsheet, database and programming language. Plain text, so it diffs and streams well. Tiny files.
XLS is stronger at: Still opens in Excel and LibreOffice.

Why convert CSV to XLS?

People make this switch when they run into the limits of CSV: the data needs formulas, formatting or multiple sheets. XLS is the better fit when a legacy system demands it specifically.

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: Hard row and column limits. Larger files than XLSX.

What is preserved when converting CSV to XLS?

The content survives; the layout is rebuilt. Text and the order it is read in carry across, but XLS lays the page out again rather than reproducing CSV's exact positioning, so line breaks, page breaks and spacing will differ. Anything that depends on precise placement is worth checking in the result.

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.

Measured, not estimated

What converting CSV to XLS actually costs

On every sample measured, the XLS came out larger — 5.7× larger at best and 15× larger at worst.

Each row is one sample chosen to isolate a property these formats treat differently.
Sample	CSV in	XLS out	Change
A plain tableTen rows of flat records — the shape almost every spreadsheet export actually has.	380 B	5.0 KB	13×
Many columnsForty columns across three rows. Column-heavy data is where per-cell overhead shows up.	1.3 KB	7.5 KB	5.7×
Nested recordsObjects inside objects. This is the shape that cannot survive a flat format intact, and the one that triggers a warning.	301 B	4.5 KB	15×
Commas and quotation marksText fields containing the delimiter and the quote character — where an escaping bug would show.	875 B	5.5 KB	6.4×

Produced by this site's own converter. The same code that runs in your browser, at the same default settings, so these are the bytes you would download.

Samples are generated from a fixed seed rather than taken from real photographs or documents, so the corpus is reproducible and carries no licensing question — and so the numbers predict the shape of your result rather than its exact size. Measured 2026-10-01. The method, and the command that regenerates every figure on this page, are on the how it works page.

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

Legacy Excel Workbook

Excel's pre-2007 binary workbook.

Extensions: .xls
MIME type: application/vnd.ms-excel
Best for: Legacy systems that reject XLSX
Compatibility: Still opens in Excel and LibreOffice.

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

Good to know

CSV to Excel (XLS) Converter — questions

How do I convert CSV to XLS?

Drop your CSV file onto the area above, then press Convert. The XLS file saves straight to your device. You do not need an account, and there is no watermark.

Is it safe to convert CSV files here — are they uploaded to a server?

No, nothing is uploaded. On most online converters, pressing the button copies your file across the internet onto a computer owned by that website; it is converted there and sent back. That copy is what "upload" means, and it is the part that puts your file out of your control. This site does not do it. Your CSV file is read and converted by the browser you are using right now and never leaves this device, so there is no copy for anyone to store, read or hand over. You can prove it: turn off your Wi-Fi after this page loads and the conversion still works.

Can I convert confidential CSV files, like bank statements or contracts?

Yes, and that is the case this site was built for. Because the file never leaves your device, a confidential document is no more exposed than it is sitting in your own folder — there is no transfer, no copy on someone else's hardware, no retention period to read about and no staff with access. Nothing is logged about the file either: not its name, not its size, not its contents. The one thing worth saying plainly is that this protects the file in transit and at rest on our side, not from anything already on your own computer.

What should I know before converting CSV to XLS?

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

What is preserved when converting to XLS?

Text, structure and images carry over faithfully. Exact page layout does not, because XLS 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. Pick the file through your phone's file picker — Files on iOS, or Downloads on Android — including files stored in iCloud or Google Drive.