CSV to XLSX Converter — Free, No Upload
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Supported formats: .csv,.xlsx,.xls,.xlsm,.xlsb,.tsv
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How to convert CSV to XLSX
- Open your CSV. Drag your .csv file onto the converter above, or click to browse. Nothing is uploaded — it is read in your browser.
- Check the detected types. The tool assigns text, number and date types per column so codes like 007 and IDs like 01-234 keep their leading zeros. Adjust any column that was guessed wrong.
- Download the .xlsx. Click convert and save a native Excel workbook. It opens cleanly in Excel and Google Sheets with no import wizard and no macros.
About CSV to XLSX
Convert CSV to XLSX free, right in your browser — no upload. Builds a real Excel workbook with correct text/number/date types, so leading zeros, long IDs, dates and UTF-8 characters survive. Handles large files.
A plain CSV opened directly in Excel often mangles leading zeros, dates, and accented characters because Excel guesses the column types on open.
This tool builds a real XLSX workbook instead, assigning correct cell types (text, number, date) up front so codes like "007" or IDs like "01-234" stay intact.
It's the fix for the classic "Excel changed my data" complaint that hits anyone importing CSV exports into spreadsheets.
Category: Conversion & ExportCommon Use Cases
- Preparing raw CSV exports for a management report that needs to open cleanly in Excel
- Fixing the classic "Excel deleted my leading zeros" error when opening a CSV of product or ZIP codes
- Converting huge CSVs into a readable, correctly-typed spreadsheet without manual reformatting
- Turning a CSV export from an accounting or ERP system into a native XLSX ready for a finance team
- Preparing a CSV for a colleague who only works in Excel and needs real number/date formatting, not raw text
Key Features
- Assigns correct cell types (text, number, date) instead of relying on Excel auto-detection
- Preserves leading zeros, long numeric IDs, and non-Latin characters
- Generates a native .xlsx file, no macros, opens cleanly in Excel and Google Sheets
- Handles large CSVs without truncation or row limits from copy-paste workflows
- No formulas or scripts injected, output is a plain data workbook safe to share externally
The CSV to XLSX tool is compatible with: Microsoft Office 365, SharePoint, Financial Reporting.
Pair with the Multiway Converter when the same dataset also needs to go out as JSON or TSV, or with Smart Merge first if you need to combine several CSVs into one workbook before converting. Run Compress afterward if the resulting XLSX is still too large to email.
Frequently Asked Questions
Yes, it preserves UTF-8 encoding and special characters when generating the native XLSX file.
Yes, it's built to handle large files without needing to upload them to an external server.
Excel guesses column types when it opens a CSV directly and treats numeric-looking codes as numbers, dropping leading zeros. This tool assigns the correct type before the file ever reaches Excel, so codes like "007" stay intact.
Yes, date columns are assigned a proper date type rather than being left as text or misread as a different locale's date format.
No, the generated .xlsx is a plain data workbook with no macros, so it's safe to open and share without security warnings.
For a single dataset, use this tool directly; for many files at once with the same cleanup applied, use Batch Processor and export as XLSX.
Aimed at analysts and accountants who are tired of re-typing IDs Excel silently stripped of leading zeros.
Read the related guide →