Private, local-first data tools
Use this CSV to Excel converter to create an XLSX or legacy XLS workbook locally. Preview the columns first and preserve text values such as leading-zero account codes.
The parser runs off the main thread. Once loaded, you can search, sort, validate, repair and export without an account.
A customer number is not necessarily a quantity. Before converting a customer list, payment export or inventory file, identify the columns whose exact characters matter. The original CSV is your reference: a workbook cannot recover digits that were already removed before you uploaded the file.
When Excel interprets imported text as a number, 00120 can become120. A long identifier may appear in scientific notation, and numeric precision is limited to 15 significant digits. Scientific display alone does not prove lost data; check the underlying value. Once digits have been rounded away, changing the display format cannot restore them.Microsoft explains these conversions and their limits.
Excel for Microsoft 365 and Excel 2024 on Windows and Mac offer Automatic Data Conversions settings. Do not assume the same controls exist in older versions. When importing through Power Query, set identifier columns to Text before loading them. If you only need a readable workbook, the converter above writes CSV values as text cells directly.
account_id,long_identifier,postal_code
000184,12345678901234567890,00120This is the first data row from theleading zeros fixture. Exporting it produces text cells containing 000184,12345678901234567890 and 00120. Automated tests read the generated XLSX and XLS bytes back and check both the complete values and their text cell types. These are export checks, not a claim that every desktop Excel version was tested.
The same policy applies to amounts and dates: 12.50 and2026-09-01 remain text. A value such as =1+1 is written as literal text, not a spreadsheet formula. You may need to convert a genuine amount column to numbers in Excel before calculating totals. Leave account numbers and postal codes as text. This follows SheetJS cell typing: string inputs produce text cells.
A byte order mark can help Excel recognize a UTF-8 CSV when opening it directly. Without a BOM, an explicit Text/CSV import can still read UTF-8 correctly; adding one is not universally required.Microsoft documents both opening routes. A BOM does not preserve leading zeros or tell Excel which columns are text.
The workbench's BOM checkbox affects CSV downloads. XLSX is a workbook container with Unicode worksheet text, so it does not use that CSV encoding option. If names already look garbled in the preview, correct the source encoding before conversion using theCSV encoding guide.
Choose XLSX for current spreadsheet applications. Choose XLS only when the receiving application requires that older format. Their worksheet capacities differ, as listed in SheetJS's format limits:
| Output | Format capacity | CSV Dock limit |
|---|---|---|
| XLSX | 1,048,576 total rows; 16,384 columns | 250,000 retained data rows; 16,384 columns |
| XLS | 65,536 total rows; 256 columns | 65,535 data rows plus the header; 256 columns |
Export stops if a worksheet exceeds its row or column capacity. A source beyond the workbench's retention limit also blocks export, rather than saving its preview. Large files can be inspected with the CSV viewer or divided using Split CSV. Before handing off a workbook, compare record counts and sensitive identifiers with the source; use theCSV validator for malformed rows and theleading zeros guide for a focused checklist.
What this tool does
This CSV to XLSX converter parses the CSV as text, presents its detected structure, then creates a real Excel workbook inside the same browser worker. A CSV to XLS option is also available for older applications. It is a safer way to open a CSV file in Excel when delimiter, encoding or text-value guesses could damage the data. Text cells stay text by default, which protects leading zeros and long identifiers.
Local files are read by a dedicated browser worker and are not uploaded to an application server. File contents and filenames are not included in analytics events. Loading a public URL is an explicit direct request from your browser and may fail when the remote server blocks CORS.
No. Renaming .csv to .xlsx does not create an Excel workbook. Parse the CSV with this converter and download XLSX to produce the workbook format; choose XLS only when a legacy application requires it.
Choose the CSV, verify its encoding, delimiter and header in the preview, then download XLSX for current Excel or XLS only for older software.
The generated workbook writes CSV values as text, so values such as 000184 remain unchanged.
Use XLSX for current Excel, Numbers and LibreOffice. XLS is provided only for compatibility with older software.
The page is online, but the file conversion itself runs locally in your browser and does not upload the CSV.
Yes. The browser converter creates the XLSX locally without an account, an upload or a paid conversion step.
Open the CSV here, confirm the detected encoding and delimiter, then save it as XLSX. Excel opens the generated workbook directly without guessing how the raw CSV columns are separated.
Yes. Choose XLSX for current Excel or select XLS only for older software. Both files are generated from the verified CSV preview in your browser.
A CSV stores values and delimiters, not fonts, colors or cell styles. Convert it to XLSX first to add Excel formatting; this tool preserves the table data but does not invent styles or formulas.