Excel to CSV Converter

How to Convert Excel to CSV

Click the file input and select an .xlsx spreadsheet from your computer. The tool reads the file entirely within your browser, parses the internal ZIP and XML structure, and extracts the cell values from the first worksheet. A spreadsheet-style preview appears so you can verify the data looks correct. The CSV output populates automatically in the text area below, ready to copy or download.

If you need a delimiter other than commas, switch the dropdown to tab, semicolon, or pipe. The CSV output regenerates immediately with the new delimiter. Fields that contain the delimiter character, double quotes, or line breaks are automatically wrapped in quotes following the RFC 4180 convention, which ensures the output can be parsed correctly by any CSV-aware application.

What Happens Inside the .xlsx File

An .xlsx file is not a single document. It is a ZIP archive containing a collection of XML files that describe the workbook, its worksheets, shared string tables, styles, and relationships between components. When you upload a file, the tool decompresses this archive using the browser's built-in DecompressionStream API, locates the worksheet XML, and reads each cell's value along with its data type.

String values in Excel are often stored in a shared string table rather than directly in the worksheet. This is an optimization that avoids repeating the same text across many cells. The converter resolves these references automatically, replacing index numbers with the actual text content. Numeric values, booleans, and inline strings are extracted directly from the worksheet XML.

How Formulas Are Handled

Excel stores both the formula expression and its last calculated result in the worksheet XML. This converter extracts the cached result, not the formula itself. A cell containing =VLOOKUP(A2, data!A:B, 2, FALSE) will appear in the CSV as whatever value Excel computed when the file was last saved. This is the standard behavior for data export and matches what you would see if you copied and pasted values in Excel.

Why Convert Excel to CSV?

CSV is the universal interchange format for tabular data. Almost every programming language, database tool, and data pipeline can read CSV without specialized libraries. When you need to import spreadsheet data into a SQL database, a data warehouse, a CRM system, or a custom application, CSV is usually the path of least resistance. It strips away formatting, formulas, and Excel-specific features, leaving just the raw data in a format that any tool can consume.

Limitations of This Approach

The converter reads the first worksheet in the workbook. Multi-sheet workbooks will only yield data from Sheet 1. Date values stored as Excel serial numbers will appear as numbers rather than formatted dates, because the formatting information lives in the styles XML, which is separate from the cell value. If your spreadsheet relies heavily on merged cells, conditional formatting, or pivot tables, those structural features do not translate to CSV since the format only supports flat rows and columns.

Frequently Asked Questions

How does the conversion work?

The tool reads the .xlsx file as a ZIP archive in your browser, decompresses the XML files inside, parses the worksheet structure, extracts cell values, and assembles them into CSV format. No data is sent to any server.

Which Excel formats are supported?

Only .xlsx files (Office Open XML, Excel 2007 and later). The older .xls binary format uses a proprietary structure that cannot be parsed with browser APIs.

What happens to formulas?

The converter outputs the last computed values, not the formulas themselves. This is standard data export behavior, since CSV has no concept of formulas.

Can I choose a different CSV delimiter?

Yes. Select comma, tab, semicolon, or pipe from the dropdown. The CSV output updates immediately when you switch.

Is there a file size limit?

Processing happens in browser memory. Files up to 10-20 MB with tens of thousands of rows work well on modern devices. Very large spreadsheets may benefit from a desktop tool.