CSV to Excel Converter
Convert CSV/TSV files to Excel (.xlsx) format. Files are processed entirely in your browser and never sent to a server.
What Is a CSV to Excel Converter?
A CSV to Excel converter takes comma-separated (CSV) or tab-separated (TSV) plain text data and turns it into a file in Microsoft Excel's native ".xlsx" format. CSV data that looks garbled or misaligned when opened in a plain text editor — columns running together, encoding artifacts, no visual structure at all — becomes a properly formatted, ready-to-read table the moment it's converted.
Every step of the conversion happens locally, right inside your browser. Nothing you paste or upload is ever transmitted to a server for processing. That means even sensitive spreadsheets — customer contact lists, internal sales figures, payroll exports, or anything else you wouldn't want to send over the internet — can be converted with complete peace of mind, since the data never leaves your device.
How to Convert CSV to Excel
- Choose the delimiter that matches your data Select comma-separated or tab-separated depending on how your source file is formatted. If you're not sure which one you have, load the sample data first to see what each delimiter looks like.
- Paste your CSV or TSV data Paste the raw text directly into the input textarea, or click "Load Sample" to see the tool in action with example data before using your own.
- Check the formatted preview Review the table preview that appears as you type. Look closely for columns that don't line up correctly or characters that appear garbled — both are signs the delimiter or source encoding needs a second look.
- Download the Excel file Once the preview looks correct, click the download button to save the result as a ready-to-open .xlsx file on your device.
Tips for getting more out of it
- The sheet in the generated Excel file is always named "Sheet1". If you need multiple sheets, adjust them manually in Excel after downloading.
- If the source CSV file uses an encoding other than UTF-8 (such as Shift-JIS), the converted text may appear garbled. We recommend re-saving the file as UTF-8 before converting it.
- After conversion, Excel may automatically interpret cell contents as numbers or dates (for example, "1-2" becomes a date). If you have columns that must keep leading zeros, such as postal codes or product codes, set that column's format to "Text" in Excel after conversion.
- File contents are processed entirely in your browser (client-side) and are never uploaded to a server, so it's safe to use even with sensitive data.
When This Tool Comes In Handy
Sharing exports from legacy or internal systems
Many in-house business systems and older databases can only export data as CSV. When a colleague, client, or manager only works in Excel, converting first avoids back-and-forth confusion over "the file won't open right."
Fixing encoding trouble from overseas SaaS exports
CSV files exported from software built outside your region sometimes use an encoding that displays as broken characters when double-clicked open in Excel. Converting through this tool first gives you a working Excel file without needing separate encoding-repair software.
Preparing raw data for filtering, sorting, or charts
Rearranging rows, applying filters, or building a chart directly from a raw CSV file in a text editor simply isn't possible. Converting to .xlsx first gives you a real spreadsheet where Excel's built-in tools work as expected.
Handling codes with leading zeros, like postal or product codes
If your data includes columns such as postal codes or product codes that begin with zero, the typical workflow is to convert to Excel first, then set that column's cell format to "Text" inside Excel so the leading zeros aren't silently stripped away.
Glossary
- CSV
- Short for Comma-Separated Values — a plain text format where each line represents a row and commas separate the individual column values.
- TSV
- Short for Tab-Separated Values — functionally identical to CSV, except a tab character is used to separate columns instead of a comma. Useful when the data itself contains commas.
- xlsx
- The default file format for Excel 2007 and later, based on the Office Open XML (OOXML) standard. Structurally, it's a ZIP archive containing a set of XML files that describe the workbook's sheets, styles, and data.
- Character encoding
- The scheme used to represent text as bytes. If a source CSV file was saved in an encoding other than UTF-8 (such as Shift-JIS), converting it can result in garbled, unreadable characters in the output.
- Cell format
- The display rule Excel applies to a cell's contents — as a number, date, or plain text, for example. Setting a column's cell format to "Text" after conversion is the standard way to preserve leading zeros that Excel would otherwise strip.
Frequently Asked Questions
Side Note — Why Does Excel "Break" CSV Data?
The problem of Excel silently converting values into dates when you open a CSV file has plagued data engineers worldwide for years. Strings like "1-2" or "3/4" get automatically reinterpreted as dates, with no easy way to recover the original text. Microsoft has been aware of the issue since the 2010s, but backward compatibility has made a proper fix difficult; it wasn't until a 2021 update that Excel finally added the ability to specify a column's type during import.
This problem was most damaging in the field of genomics research. A 2004 study found that roughly 20% of gene name lists published in academic papers had been corrupted by Excel's autocorrection — for example, the gene name "SEPT2" (Septin-2) being converted into "2-Sep" (September 2). In response, the HUGO Gene Nomenclature Committee took the unusual step in 2020 of renaming genes that were especially prone to this kind of corruption.
The ".xlsx" format used by Excel today is actually a ZIP-compressed collection of multiple XML files (Office Open XML, or OOXML). Adopted starting with Office 2007, this format's specification is publicly documented, unlike the older proprietary binary ".xls" format, which makes it far easier for other software to read and write. This open specification is a major reason why open-source libraries like SheetJS — which this tool uses — can generate .xlsx files even without Excel installed.