Free Excel and CSV tools that run in your browser
Convert between CSV, XLSX and JSON, merge workbooks, remove duplicate rows and explore large CSV files. Nothing is uploaded: your spreadsheets are read and written locally, on your own device.
CSV to Excel
Turn CSV, TSV or TXT files into a real .xlsx workbook, keeping leading zeros.
Excel to CSV
Save any sheet of an .xlsx workbook as CSV, with the delimiter you need.
Excel to JSON
Turn a sheet into a JSON array of objects, using the first row as keys.
JSON to Excel
Turn a JSON array into an Excel or CSV table, flattening nested objects.
Merge Excel files
Stack rows from several workbooks into one sheet, or keep a sheet per file.
Remove duplicate rows
Delete repeated rows from Excel or CSV, comparing whole rows or chosen columns.
CSV viewer
Open big CSV or Excel files as a table you can sort, filter and export.
Column letter converter
Convert Excel column letters to numbers and back, and decode cell addresses.
How these spreadsheet tools work
The tools read your file in a background worker, transform the table in memory and give you the result as a download. Because nothing travels over the network, they are safe to use with customer lists, payroll exports and other sensitive data. The page stays responsive even with files of hundreds of thousands of rows.
What you can do
Turn a CSV export into a proper workbook without losing leading zeros, or save any sheet as CSV with the delimiter your system expects. Convert sheets to JSON for code and APIs, or flatten JSON back into a table. Stack monthly exports into one sheet, remove repeated rows by the columns that matter, and sort and filter a large CSV without opening a spreadsheet program.
Formats and limits
The tools work with modern .xlsx workbooks, .csv, .tsv and JSON. Values are preserved, but formulas become their last calculated result and formatting, charts and macros are not carried over. Legacy .xls files and password-protected workbooks need to be re-saved as plain .xlsx first.