AnyFormat

00 CSV → XLSX

CSV to XLSX

A real Excel workbook with typed cells and sized columns.

01CSV in
02XLSX out
03Options 4

Exports from European versions of Excel use semicolons, because the comma is the decimal point there.

Off means rows come out as arrays instead of objects.

Off keeps every value as a string — safer for IDs, postcodes and phone numbers with leading zeroes.

  • No upload The conversion runs in this tab. Your file never travels — not to us, and not to the advertising.
  • No sign-up, no email, no daily cap There is no account system to sign up to.
  • No size limit we invented Only your device's memory — about ~2 GB on a desktop browser, ~400 MB on a phone.
  • Turn your Wi-Fi off and convert anyway The conversion needs nothing but this page. Ads will not load without a connection; your file will still convert. That is the whole claim, and it takes five seconds to check.

Drop a CSV and get a genuine .xlsx workbook — not a CSV with the extension changed, which is what several online converters produce and what makes Excel show a warning dialog every time the file is opened.

Why not just rename the file

Excel will open a renamed CSV, but it complains that the format does not match the extension, it re-parses the file with your locale's separator rules every time, and nothing about the file is preserved when it is shared. A real XLSX is a ZIP of XML that records cell types, column widths and a sheet name.

Cell types

Values that are numbers become numeric cells, so they right-align, sum and sort correctly. Booleans become boolean cells. Everything else is text.

The catch is the same one as CSV to JSON: an ID like 02134 is numerically 2134. If your file has identifiers, postcodes or account numbers, switch off Detect numbers and booleans and every column comes through as text with its formatting intact.

Column widths and row limits

Columns are sized to their content up to a sensible maximum, so you do not open the file to a screen of ####. Excel's own hard limit of 1,048,576 rows applies — a CSV longer than that is refused with the exact count rather than being silently truncated at the boundary.

Other names for this

Also searched as “csv to excel”, “convert csv to xlsx”, “csv to spreadsheet”.

Questions

Is this a real Excel file?
Yes — a valid XLSX package (ZIP of XML) that Excel, LibreOffice, Numbers and Google Sheets all open natively with no warning.
My postcodes lost their leading zeroes.
Turn off “Detect numbers and booleans” so every column is written as text.
Can I put several CSVs into one workbook as separate sheets?
Not yet — each file becomes its own workbook. Drop several and you get several files, each keeping its original name.
Is my data uploaded anywhere?
No. The conversion runs as JavaScript inside this tab. Open your browser's Network panel and convert something — you will see no request carrying your data, because there is no server to send it to. You can also turn your Wi-Fi off and convert anyway.
How large a file can I convert?
There is no imposed limit — the ceiling is your device's memory. In our testing a desktop browser handles files up to about 2 GB and a phone up to about 400 MB before the tab runs out of memory. Files above a few hundred megabytes are noticeably slower because everything is held in RAM at once.