Zip codes & phone numbers
Stop "00123" turning into 123. XLSX preserves leading zeros via text-typed cells without an apostrophe hack.
Free CSV to Excel Converter Online (.xlsx & .xls)
Convert CSV files to Excel (.xlsx) spreadsheets instantly in your browser.
Processed in your browser. Nothing uploaded.
Drop a CSV file here or click to browse
CSV (comma-separated values) files
All processing happens in your browser. No files are uploaded.
What Is CSV to Excel Conversion?
CSV to Excel is a free online tool that convert CSV files to Excel (.xlsx) spreadsheets instantly in your browser. No files are uploaded — everything is processed locally on your device.
CSV to Excel conversion takes a plain-text Comma-Separated Values file (defined by IETF RFC 4180) and produces a properly typed Excel workbook in the modern .xlsx format. .xlsx is the Office Open XML format introduced in Office 2007, defined by ECMA-376 and ratified as ISO/IEC 29500 in 2008. It supports up to 1,048,576 rows and 16,384 columns per sheet, which is 16 times the row capacity of the legacy .xls binary format (65,536 rows max). The reason to convert rather than simply opening the CSV in Excel comes down to data preservation. CSV is text-only and carries no type metadata, so Excel applies several silent transformations on import: leading zeros disappear ("00123" becomes 123, breaking ZIP codes and product SKUs), values that look numeric but contain dashes get parsed as dates ("3-4" becomes March 4th), long numeric strings collapse to scientific notation ("1234567890123" becomes 1.23E+12), and on Windows installs without a UTF-8 BOM the encoding falls back to Windows-1252 and mojibakes accented characters. A real .xlsx file declares each cell's type explicitly, so all of these stay intact. This CSV to XLS / XLSX converter runs entirely in your browser. Drop a .csv file (any delimiter: comma, semicolon, tab, or pipe), the parser auto-detects the format and encoding, and the output is a properly typed Excel workbook ready for download. Multi-sheet workbooks, formulas, and cell formatting are all preserved on the way in. No upload, no signup, safe for sensitive financial, medical, or business data. Whether you call it a CSV to Excel converter, a CSV to XLS converter, a CSV Excel converter, or simply need to convert CSV to Excel online — it is the same tool, and it works for any CSV file format.
Privacy guarantee: CSV to Excel processes all files directly in your browser using WebAssembly. No data is uploaded to any server, no information is collected, and the tool works offline after loading. Unlimited usage with no signup, no watermarks, and no file size limits.
How to Use CSV to Excel
Upload your CSV file
Select a CSV file from your device or drag it into the upload area. Any delimiter (comma, semicolon, tab) is auto-detected.
Configure parsing options
Review the parsed data table. Adjust column types, delimiter settings, or encoding if needed.
Download Excel file
Click Convert to generate and download the .xlsx spreadsheet file.
Why Use Our CSV to Excel Converter?
Auto-detects delimiters (comma, semicolon, tab, pipe) and encodings
Preserves data types — numbers stay as numbers, dates as dates
Generates proper .xlsx files with formatted columns and headers
Browser-based — sensitive data never leaves your device
Handles large CSV files with thousands of rows efficiently
No signup, file size limits, or conversion caps
Powered by SheetJS for reliable, Excel-compatible output
Advanced Guide: CSV to Excel
CSV vs .xlsx vs .xls, Specs and Why It Matters
.xlsx is the modern Office Open XML format defined by ECMA-376 (December 2006) and ISO/IEC 29500 (2008), introduced in Office 2007. The legacy .xls is a binary BIFF8 format from Excel 97–2003. The format choice changes both capacity (16× more rows in .xlsx) and how Excel handles encoding, leading zeros, and dates, the four most common CSV-import bugs.
- .xlsx capacity: 1,048,576 × 16,384 — Rows × columns per sheet; supports unlimited sheets per workbook
- .xls (legacy) capacity: 65,536 × 256 — BIFF8 binary, Excel 97–2003. 16× fewer rows than .xlsx
- Locale delimiter: Comma (en-US) / Semicolon (EU) — Excel reads the OS "List separator", wrong delimiter splits everything into column A
- UTF-8 + BOM: Required (Windows) — Without `EF BB BF`, Excel for Windows decodes as Windows-1252 and breaks accents
| Pain Point | .xlsx Solution | Why |
|---|---|---|
| "00123" becomes 123 | Text-typed cells (`t="s"`) | XLSX explicitly types each cell, so leading zeros and codes survive (ECMA-376 §18.18.11) |
| "3-4" becomes a date | Text-typed cells | CSV has no type metadata; XLSX cell types prevent silent date coercion |
| Garbled accents (mojibake) | Built-in UTF-8 | XLSX always uses UTF-8 internally; no BOM debate |
| Wrong delimiter on EU machines | Locale-independent | XLSX is structured XML, not delimited text, opens identically anywhere |
| Need formulas / formatting | Native XLSX support | CSV is text-only; XLSX preserves formulas, fills, fonts, column widths |
| Multiple related tables | Multi-sheet workbook | CSV is one table per file; XLSX supports unlimited sheets |
| Email attachment | Either, XLSX often smaller | XLSX is ZIP-compressed, so large CSVs often shrink 60–80% on conversion |
High-Intent CSV-to-Excel Use Cases
European spreadsheets
Avoid the semicolon-vs-comma headache for users on de-DE / fr-FR / es-ES Excel installs.
Accented names & multilingual data
Names, addresses, and product titles in Spanish, French, German, or Vietnamese render correctly without BOM gymnastics.
Multi-table reports
Combine raw CSV + summary sheet in one workbook for stakeholders who want both.
Locked data tables
Add cell formats, merged headers, and frozen panes that CSV cannot represent.
Date formatting
Lock dates as `YYYY-MM-DD` text rather than letting Excel re-interpret them by locale.
Frequently Asked Questions
Why not just open the CSV file directly in Excel?
Opening a CSV in Excel often causes data corruption: long numbers become scientific notation (e.g., "1234567890123" becomes "1.23E+12"), leading zeros are stripped from IDs and ZIP codes, and dates in non-US formats are misinterpreted. This converter preserves data types correctly.
What delimiters does this tool support?
The converter auto-detects commas, semicolons, tabs, and pipe characters as delimiters. You can also manually select the delimiter if auto-detection doesn't match your file format.
Can I convert multiple CSV files at once?
Currently the tool processes one CSV file at a time. Each CSV is converted to a single-sheet Excel workbook. For batch conversion, process files one after another.
Is my data safe during conversion?
Yes. All processing happens locally in your browser using SheetJS. No data is sent to any server. This makes it safe for confidential business data, financial records, and personal information.
How do I convert CSV to Excel online for free?
Drop your .csv file (or paste CSV text), let the converter auto-detect delimiter and encoding, then click Download to get an .xlsx file. There is no upload, no signup, no email gate. You can also download as legacy .xls if your recipient is on Excel 97–2003.
Can I convert CSV to .xls (legacy Excel) instead of .xlsx?
Yes — choose .xls in the format dropdown. Note the legacy .xls binary format caps at 65,536 rows and 256 columns, while modern .xlsx supports up to 1,048,576 rows and 16,384 columns. If your CSV has more than 65k rows, .xlsx is the only option that fits.
Will leading zeros and long numbers survive the conversion?
Yes. Cells that look like "00123" or "1234567890123" are written to the .xlsx as text-typed cells (per ECMA-376 §18.18.11), so leading zeros stay intact and long numbers do not collapse to scientific notation. This is the single biggest data-corruption issue when you simply open a CSV in Excel — converting first solves it.
Why does my CSV file converter need to handle UTF-8 BOM?
Excel for Windows decodes CSV as Windows-1252 by default unless the file starts with the three-byte UTF-8 BOM (`EF BB BF`). Without the BOM, accented names, addresses, and product titles render as mojibake. This converter writes the BOM into intermediate CSV exports, but more importantly the .xlsx output uses UTF-8 internally per ECMA-376, so encoding issues disappear entirely.
What does this csv excel converter do that opening directly in Excel does not?
Three things: (1) preserves leading zeros and long numbers as text, (2) prevents date coercion of values like "3-4" or "1/2", (3) fixes encoding so accented characters render correctly on Windows. It also supports any delimiter and produces a real .xlsx — not a CSV with an .xls-renamed extension.
More Data Tools
JSON to CSV
Convert JSON to CSV online free. Paste or upload JSON arrays and download CSV files instantly.
CSV to JSON
Convert CSV data to JSON arrays instantly in your browser.
XML to JSON
Convert XML documents to JSON format in your browser — no server needed.
JSON to XML
Convert JSON data to XML format instantly in your browser.
YAML to JSON
Convert YAML to JSON format instantly in your browser.
Markdown to HTML
Convert Markdown text to HTML code instantly in your browser.
HTML to Markdown
Convert HTML code to Markdown format instantly in your browser.
Markdown to PDF
Convert Markdown files to beautifully formatted PDF documents in your browser.
Popular Free Tools
Merge PDF — Free Online
Combine multiple PDF files into one document — entirely in your browser, no uploads.
Compress Image — Free Online
Reduce image file size while preserving quality — no uploads, browser only.
QR Code Generator — Free Online
Generate QR codes for URLs, text, email, and more — entirely in your browser.
JSON Formatter — Free Online
Format, validate, and minify JSON data in your browser. Supports syntax highlighting.
MP4 to MP3 — Free Online
Extract audio from video files and save as MP3, entirely in your browser.
Password Generator — Free Online
Generate strong, random passwords with customizable length and character sets.
Hash Generator — Free Online
Generate SHA-1, SHA-256, SHA-384, and SHA-512 hashes from any text — entirely in your browser.