Online tools
Excel to CSV converter (UTF-8, no upload)
A free Duaer tool that turns .xlsx or .xls into UTF-8 CSV in your browser. Pick a sheet; a BOM is added by default so Excel reopens it cleanly.
How to use it
- Drop the file into the box above, or click "choose a file".
- Check the preview to make sure rows and columns line up.
- Click "Download .csv".
- If the workbook has several sheets, pick the one to export from the drop-down first.
Conversion rules
- Cells are exported as Excel displays them: dates, percentages, and thousands separators keep their format.
- Blank rows are skipped; merged cells keep the value in the top-left cell only.
- BOM: on by default. Untick it when the CSV goes into a database or a script.
Automate it in Duaer
In Duaer, Extract from File › Extract From XLSX reads each row as an item. Follow it with Convert to File › Convert to CSV, or write the rows straight into Google Sheets or a database.
Questions
What is a BOM, and do I need it?
A BOM is three bytes at the start that tell Excel the file is UTF-8. Keep it when people open the CSV in Excel; for imports, Duaer suggests following what the target system expects.
Can it read old .xls files?
Yes. The Duaer converter reads .xlsx, .xlsm, .xls, and .ods.
In this section
Free file converters from Duaer
Free Duaer tools for spreadsheets and data files: convert formats, merge, split, remove duplicates, fix encodings, and format JSON. Everything runs in your browser and no file is uploaded.
File conversionCSV to Excel converter (free, no upload)
A free Duaer tool that turns CSV into .xlsx in your browser. It detects UTF-8 or GBK, keeps long IDs as text, and never uploads the file.
File conversionJSON to CSV converter (nested JSON flattened)
A free Duaer tool: paste or upload JSON, nested fields become columns, and you download CSV or Excel. It runs in your browser with no upload.
File conversionCSV to JSON converter (free, no upload)
A free Duaer tool that turns each CSV row into a JSON object keyed by the header row. Optional number and boolean detection, GBK support, copy or download.
Office tasksMerge several Excel files into one sheet with Duaer
In Duaer, upload several xlsx files, read every row, tag each with its source file, remove duplicates, and export one combined sheet. No formulas and no AI credits.