File & Format Converters · Free tool
CSV to Excel Converter
Convert CSV to a real Excel file (.xls SpreadsheetML 2003 format) that Excel, Google Sheets, and LibreOffice all open natively. No upload, no signup, no library bloat.
Updated May 2026
Delimiter
Comma (,)
Output is SpreadsheetML 2003 (.xls extension). Excel, Google Sheets, and LibreOffice all open it. Excel may show a warning the first time (“The file format and extension don’t match”) — click Yes to open. For more advanced Excel features (formulas, multiple sheets, charts) save as native .xlsx after opening.
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What it does
Convert CSV to a real Excel file that opens natively in Excel, Google Sheets, and LibreOffice. Uses SpreadsheetML 2003 format (.xls extension) — a single XML file rather than the ZIP-of-XML XLSX format, which means no library dependencies and a tiny bundle.
Output preserves: header bold formatting, number vs string column types (auto-detected), and clean column alignment. For advanced features like formulas, multiple sheets, or charts, save as native .xlsx after opening in Excel.
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<iframe src="https://freetoolarena.com/embed/csv-to-excel-xml" width="100%" height="720" frameborder="0" loading="lazy" title="CSV to Excel Converter" style="border:1px solid #e2e8f0;border-radius:12px;max-width:720px;"></iframe>How to use it
- Paste your CSV in the input.
- Set a filename (no extension needed).
- Preview the table to verify rows parsed correctly.
- Click Download — the .xls file opens in Excel / Sheets / LibreOffice.
Frequently asked questions
- Why is the output .xls and not .xlsx?
- True XLSX requires a ZIP-of-XML library (~700KB minified) which we don't want to add for one tool. SpreadsheetML 2003 (.xls extension) is a single XML file Excel and Sheets both open natively. Excel may show a warning the first time — clicking Yes opens it. To convert to true XLSX, just save-as in Excel after opening.
- Will Excel warn that the file format doesn't match?
- On modern Excel (2016+), yes — a one-time warning saying 'The file format and extension don't match'. Click Yes to open. Google Sheets and LibreOffice open without warning. The format is genuinely an Excel format, just an older one.
- Does it handle quoted CSV with commas in fields?
- Yes — the CSV parser handles RFC 4180 quoting: values in double quotes preserved verbatim, embedded quotes escaped as "", newlines inside quotes preserved. Quoted commas are not treated as delimiters.
- Does it auto-detect numeric columns?
- Yes — values matching the pattern -?\d+(\.\d+)? are typed as Number in the output, so Excel right-aligns them and lets you do math directly. Anything else is typed as String.
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Formula
Parse CSV with RFC 4180 quoting (double-quoted values support embedded commas, newlines, and escaped quotes via ""). Auto-detect numeric vs string columns: if a value matches /^-?\d+(\.\d+)?$/ it is typed as Number. Wrap in SpreadsheetML 2003 XML (single-file Excel format) with a Workbook → Worksheet → Table → Row → Cell hierarchy. Header row gets a bold style. Output as Blob with MIME type application/vnd.ms-excel and .xls extension.
What this assumes
RFC 4180 CSV. First row is treated as header. Numeric detection is conservative — only plain integers and decimals; scientific notation or thousand-separators stay as strings. SpreadsheetML 2003 is a deprecated-but-still-supported Excel format that opens in Excel, Google Sheets, and LibreOffice without a library dependency. Excel may warn about the file format mismatch on first open — clicking Yes opens it normally.
Sources
Learn more
Guides about this topic
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