CSV to Excel Converter
Convert CSV files to downloadable XLSX spreadsheets in your browser, with leading zeros preserved and no file upload. Also reads tab-separated files.
Drag .csv, .tsv or .txt files in, paste, or click to choose
A whole folder works too · Ctrl/Cmd+V pastes · on phone this opens your file picker
CSV to Excel cell type rules
| CSV value | XLSX cell type |
|---|---|
| 123 or -12.5 | Number |
| 00123, 1234567890123456, +441234567890 | Text |
| 2026-10-02 | Text; dates are not converted |
| =SUM(1,2), +name, -name, @name | Text; never formulas |
| Any value with Keep everything as text | Text |
Worksheet limits follow Microsoft’s Excel specifications and limits. Quoted fields follow the conventions documented in RFC 4180. XML special characters are escaped and XML-disallowed control characters are removed from text.
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How to convert CSV to Excel
Choose one or more CSV files, review the delimiter and cell type options, then press Convert to XLSX. Each file becomes one workbook with one worksheet named after the source file. The CSV to Excel converter reads quoted fields, doubled quotes and line breaks inside fields. Automatic delimiter detection counts commas, semicolons and tabs outside quoted fields in the first 20 records; choose a delimiter manually if the guess does not fit your file. UTF-8 decoding is tried first, including files with a UTF-8 BOM. If decoding fails, the browser reads Windows-1252 and labels the result accordingly. That fallback does not guarantee correct text for other encodings. Parsing and XLSX packaging run in a worker so the page stays usable during conversion. The download list reports rows, columns and output size for each file. Multiple workbooks can be downloaded together as a ZIP, or individually.
CSV to XLSX limits and data handling
- Output is .xlsx only, not the older .xls format. Dates remain text; this tool does not infer dates or formulas and does not repair malformed CSV.
- Excel worksheets support 1,048,576 rows and 16,384 columns. A file exceeding either limit produces an error instead of being truncated. Rows with different field counts are kept as supplied; missing cells are blank.
- Detect numbers recognises only complete numeric cells with an optional minus sign and decimal point. Leading-zero identifiers, integers longer than 15 digits and values beginning with + remain text. Keep everything as text preserves all cells as strings.
- Treat first row as header makes that row bold and freezes it; it does not remove the row. Column widths use the first 100 rows and are capped at 60 characters. Large files still need enough device memory for their rows and workbook XML.
Questions about CSV to Excel conversion
Are leading zeros preserved when I convert CSV to Excel?
Yes. Values such as 00123 stay text even with Detect numbers selected. Integers with more than 15 digits and + prefixed phone numbers also stay text. Dates remain text rather than being converted into Excel date serials.
Can CSV values become Excel formulas?
No. Values starting with = are stored as text, never as formulas. Text beginning with +, - or @ is also written as a string. A complete negative number can be stored as a number when Detect numbers is selected.
Is my CSV uploaded, and can I download multiple files?
Files are read and converted entirely in your browser. Nothing is uploaded. Download one XLSX directly or select several files and download the finished workbooks together in a ZIP.
Why does a result say Windows-1252?
The file could not be decoded as valid UTF-8, so Windows-1252 was used. Review the resulting text if the source uses another encoding; this converter does not identify every encoding automatically.
