Convert Excel spreadsheets to CSV with sheet selection and preview. Free, private, runs in your browser.
100% private — your files and text never leave your browser. All processing happens locally on your device.
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XLSX is Microsoft Excel's modern spreadsheet format, containing multiple sheets, formulas, formatting, charts, and embedded objects. CSV (Comma-Separated Values) is a plain-text format that stores tabular data as rows of comma-delimited values. Converting XLSX to CSV extracts the raw data from a spreadsheet into a universal format that can be imported into databases, data analysis tools, programming languages, and any application that processes tabular data.
CSV is the lingua franca of data. While Excel files are great for human viewing and editing, many systems require CSV for data import — databases (MySQL, PostgreSQL), programming languages (Python pandas, R), data pipelines (ETL tools), machine learning frameworks, and API integrations. CSV files are also significantly smaller than XLSX files since they contain only raw data without formatting, formulas, or metadata. Converting to CSV ensures maximum compatibility across tools and platforms.
The tool uses ExcelJS, a maintained pure-JavaScript spreadsheet library, to read your XLSX file entirely in the browser. It extracts the data from each sheet, reads formulas as their stored calculated values, and generates clean CSV output. For multi-sheet workbooks, a dropdown lets you select which sheet to convert, or download all sheets as separate CSV files. You can configure the delimiter (comma, tab, semicolon, pipe) and preview the data in a table before downloading. Legacy .xls workbooks (Excel 2003 and earlier) are not supported — re-save them as .xlsx in any spreadsheet app first.
Completely. Your spreadsheet is parsed entirely in your browser — no file upload, no server processing, no cloud storage. Spreadsheets often contain sensitive business data, financial records, or personal information. With Convertful, that data never leaves your device.
Modern .xlsx workbooks (Excel 2007 and later) are supported. Legacy .xls files from Excel 2003 and earlier need to be re-saved as .xlsx in any spreadsheet app first.
A sheet selector dropdown lets you choose which sheet to convert. You can also download all sheets as separate CSV files.
Formula cells are exported with their calculated values, not the formula strings. The CSV contains the final computed data.
Yes. Your spreadsheet is parsed entirely in your browser using JavaScript. No files are uploaded to any server.