Why not just open the CSV in Excel?

You can, but Excel guesses as it imports: it strips leading zeros, turns "1/2" into a date, rounds long numbers and splits on the wrong delimiter in many locales. Converting first produces a workbook whose cells are already typed the way you intended.

Are leading zeros kept?

Yes. Only values that are clean numbers become numeric cells; everything else, including codes like 00123 and long identifiers, is stored as text so it survives untouched.

Does it accept semicolon or tab-separated files?

Yes. The delimiter is detected from the file, so semicolon exports from European Excel and .tsv files work without settings.

How many rows can the workbook hold?

Up to Excel's own limit of 1,048,576 rows per sheet. In practice very large files are limited by your device's memory, since the CSV and the workbook are both held in RAM.

Can several CSV files be combined into one workbook?

Not with this tool. Each CSV becomes its own .xlsx with a single sheet called Sheet1. Convert up to five at once and download them as a ZIP.

Do I need Excel installed?

No. The workbook is written by code in your browser, and the result opens in Excel, Numbers, Google Sheets and LibreOffice.

CSV to Excel Converter — CSV to XLSX, Free, Private

Convert CSV to Excel (XLSX)

Turn a CSV file into a real Excel workbook with numeric cells, intact leading zeros and a bold header row. Converted on your device, so nothing is uploaded.

No upload — runs in your browser

Batch convert & ZIP download

Free, no sign-up

Drop CSV, TSV, TXT files here

Choose files

Free: up to 5 files per batch · Files never leave your device · Paste from the clipboard works too

Private by design

Your files are processed by your own device using WebAssembly and your browser's built-in codecs. Nothing is uploaded, logged or stored.

Fast & offline-ready

No queue, no waiting for a server. Once the page has loaded it even works without a connection.

Works everywhere

Chrome, Edge, Firefox and Safari on Windows, macOS, Linux, Android and iOS. No app to install.

What Excel does to a CSV, and what this does instead

Double-clicking a CSV hands the file to Excel's import heuristics, which were designed for convenience rather than accuracy. The table below shows the difference for a handful of values that cause trouble in real exports.

Value in the CSV	Excel's import guess	Tinyvert's workbook
`00123`	123	Text "00123"
`1/2`	A date in February	Text "1/2"
`4532015112830366`	Rounded to 15 digits	Text, every digit kept
`24.99`	Number (if the locale agrees)	Number
Semicolon-separated rows	One column in many locales	Delimiter detected

The rule is simple: a cell that is unambiguously a number becomes a numeric cell you can sum, sort and chart; everything else becomes text. Leading zeros and long IDs survive because they are never treated as numbers in the first place. The header row is written in bold so the sheet is readable the moment it opens.

A small example

invoice;customer;amount;due
000871;Müller GmbH;1250.00;2026-11-30
000872;Ødegaard AS;980.5;2026-12-15

This semicolon file, typical of a German or Scandinavian export, becomes a workbook whose invoice column is text (zeros intact), whose amount column is numeric, and whose accented names display correctly. XLSX stores text as Unicode internally, so there is no encoding step to get wrong.

Who converts CSV to Excel

Analysts receiving exports from Stripe, Shopify, Google Ads or a bank portal who need a file colleagues can format and filter.
Developers producing reports from a script or database query and handing them to non-technical teams.
Anyone who has been burnt by a CSV that lost its postcodes or phone numbers on the way into a spreadsheet.

A workbook also carries its types with it, so the next person to open the file does not repeat the import guesswork.

Limits worth knowing

Each CSV becomes one workbook with a single sheet named Sheet1 — there is no option to merge several files into one workbook. Excel's sheet limit of 1,048,576 rows applies, and large files are limited by your device's memory. Five files per batch are free; Tinyvert Pro, a one-time purchase, removes the batch limit.

Nothing leaves your browser

The CSV is parsed and the .xlsx is assembled by code running on your device. There is no upload, no queue and no copy kept anywhere, and the page works offline once it has loaded. For the reverse trip, Excel to CSV exports each sheet with ISO dates. Developers who need the data in code rather than a spreadsheet can use CSV to JSON, and JSON to Excel builds a workbook from an API response.

How to convert csv to excel (xlsx) — step by step

Drop up to five .csv, .tsv or .txt files into the drop zone or click "Choose files".
Conversion starts automatically — the delimiter is detected automatically and there are no settings to adjust.
Watch the progress bar, then download each .xlsx or every workbook together as a ZIP.

Frequently asked questions

Why not just open the CSV in Excel?: You can, but Excel guesses as it imports: it strips leading zeros, turns "1/2" into a date, rounds long numbers and splits on the wrong delimiter in many locales. Converting first produces a workbook whose cells are already typed the way you intended.
Are leading zeros kept?: Yes. Only values that are clean numbers become numeric cells; everything else, including codes like 00123 and long identifiers, is stored as text so it survives untouched.
Does it accept semicolon or tab-separated files?: Yes. The delimiter is detected from the file, so semicolon exports from European Excel and .tsv files work without settings.
How many rows can the workbook hold?: Up to Excel's own limit of 1,048,576 rows per sheet. In practice very large files are limited by your device's memory, since the CSV and the workbook are both held in RAM.
Can several CSV files be combined into one workbook?: Not with this tool. Each CSV becomes its own .xlsx with a single sheet called Sheet1. Convert up to five at once and download them as a ZIP.
Do I need Excel installed?: No. The workbook is written by code in your browser, and the result opens in Excel, Numbers, Google Sheets and LibreOffice.